One issue here is that from what I can cather the Xlinks project is still in the planning phase. There have been similarly ambitious projects in the EU in the past, and all were eventually shut down. In other words even the estimates there might be too optimistic. For example multi-MW scale energy storage in batteries over several hours would be as much of a first as an energy breakeven in fusion from my knowledge.
Please excuse my lack of sources, I am writing this on a phone in the middle of the night, it's just that big an issue. You should be able to verify my statements if any are in doubt, though I try my best to explain.
One simple and very clear error that you have made is about the role of nuclear in a renewable world. From an engineering perspective it is simply literally not solvable to run the grid without it. This is the lynchpin of your entire essay. All the other things do not matter if you can not replace nuclear by anything other than fossil fuels.
a) Without meaning to offend, saying that you will run the grid off of batteries is such an absolutely insane proposition that it boggles the mind, and usually comes from people in the humanities. You only worried about costs here, but the physical feasibility is literally nonexistent from an engineering and logistics point of view. Battery storage technology might work for small unincorporated communes in australia, but not for even a single industrial consumer much less a national energy grid. The difference is several orders of magnitude. A few MW demand being smoothed over for a few hours, which musks australian battery farm is capable of, is less than the demand of a single steel mill. The same battery farm by the way also failed to function in four months in 2019 for which the operator is now being sued. Normally out there ideas that musk has can be supported, but even he doesn't think this tech could carry the grid. Thinking that it could is lunacy. Apart from the lack of scale, there are other engineering issues like the incredible fire hazard, the non solved logistics of large scale (or even consumer scale) battery recycling, storage losses, capacity degradation (the australian project has only 15 years warranty), as well as the simple lack of production capacity, since we are already hitting supply chain bottlenecks for EV batteries.
b) For all the fuss about how great battery stored solar is, you unfortunately forgot to consider THEIR initial setup. Making non perovskyite solar cells and lithium batteries are two of the most toxic industrial processes with lots of waste. The only reason the extreme price decreases were possible was that china being the main producer has basically no enforced environmental regulations, with literal open lakes of toxic sludge seeping into the ground in inner mongolia.
c) Battery stored solar is NOT renewable. The earth has limited easily extractable resources of lithium and silicon. There is already a shortage of rare earth metals associated with Li Ion battery production. Last time it was Mn i think, because some processor in china could not keep up with demand but i can't find the news article. Research into alternatives is ramping up, but no good results are available yet. Global reserves could last a couple hundred years, but extraction efforts already can not keep up with current demand. If this demand increases by magnitudes by trying to store electricity in batteries even the global reserves could be used up sooner rather than later. As in we could possibly be facing peak-battery, before peak-oil.
d) Pumped hydro is complete nonsense, as even when you disregard the massive environmental destruction it causes and the potential for catastrophe, you are still left with the fact that you can only build pumped storage in very, very, VERY specific locations. You not only need a mountainous area that is high enough with steep enough slopes and a narrow enough valley, you also need a very specific ground structure beneath the topsoil for the dam structure, essentially bedrock up high in the mountains, and rocks without horizontal faults for the basin. Building even small dams on just slightly off rock has already resulted in catastrophe in the past, and worrying developments like the three gorges dam shifting. The utilization of hydroelectric potential is almost complete which you can see by there being zero new ones planned that I know of, despite the push for renewables.
e) Not only is wind about the most unpredictable thing in physics short of QM particles, solar is ALSO not predictable. For the same reason: weather. And we can not circumvent this by putting them all in the sahara, because transport losses with our current tech are enormous the sand destroys tracker servos and panel surfaces, and that's disregarding issues with security and political security. All european imported solar projects that have been proposed in the past are currently on hold, despite the push for more renewables. Someone put up xlink as an example, but that too is not yet out of the planning phase.
f) In most of the world rooftop solar is not NEARLY enough to cover the needs of the household in the winter. In most of europe you need heating running 24/7 in the winter months. Why? Because the incoming solar radiation is not enough to heat up the house. You can mitigate this by installing heatpumps in literally every single household, but it's likely that you still will not get enough energy for that, because even with fossil fueled heating, rooftop solar isn't enough to provide electricity for a family home in the winter north of the alps.
g) You could try and mitigate weather fluctuations by having a very interconnected grid on a large scale, but this is associated again with massive losses in transport, and it is also not a complete protection. What happens when there are several bad weather fronts near all solar power plants? The entire continent being under cloud cover is rare but not unheard of. So what? The energy grid goes down we freeze like the texans did last year? Except here this is would be an accepted risk, not a freak accident. Doesn't seem like an acceptable risk to me.
h) Wind as something to balance solar is a pretty good thing.... if you can build it. But windfarms require a place where windspeeds are 20+km/h to produce and where the wind is always below hurricane speeds to survive. There are entire countries where you have no suitable area for them. Nuclear plants meanwhile can be built almost anywhere.
i) Hydrogen COULD be a nice solution for energy storage, except for one thing: It is nigh impossible to store, not to mention safely. Look at how fuel cells for cars are still a tiny market and EVs have taken over precisely because of this. Granted having storage be immobile mitigates some of the risk, but getting hydrogen to not leak is a nontrivial industrial engineering challenge. Additionally massive infrastructure expansions would be needed to transition to a hydrogen based energy economy. There simply is no prototype, no precedent for grid scale hydrogen energy storage. We have small energy storage solutions with hydrogen for homes, but that's the same scale that we also have carbon recapture already available as well, and i don't see you making the point of just keeping to fossil fuels and wood burning and recapturing the carbon later. Ramping up the scale here would be similarly difficult would it not?
j) As others have already pointed out nuclear powerplants are very much capable of and engaged in regulating their output to conform to grid demands, which means that they are solving a problem that renewables create.
The above is THE biggest cluster of issues with your opinion. Until we have fusion there is simply no way around nuclear if we want to avoid fossil fuels.
A smaller but still important problem in your assessment is the only other negative side of nuclear that you mentioned: Economics.
One issue with this is that you seriously overestimate the benefits of renewables. Renewables are cheap because they are currently subsidized by many governments. Their installation as well as the price per kWh. Furthermore they are NOT easier to install than nuclear. Building a 1GW nuclear plant takes 5+ years, building a gas plant takes 2+ years, while building a simple 50MW windfarm takes 6+ months. Obviously the installation times do not scale linearly, but with 1 month for 10MW, it's a close enough estimate. So if you wanted to install separate windfarms to account for just one nuclear plant it would take you 10 years instead of 5. So i think you can't blame nuclear being cheaper on disregarded interest. And that's not covering the loss of value through making vast areas of land unfarmable with wind and solar, and the ecological damage of covering fields in darkness or in bird chopping soil compactors. Finally the biggest issue with the economic modeling is that it is not borne out by reality. Renewables are expensive. Very much so. In germany 1kWh is ~33ct in a regular tarrif, and ~31ct in a tarrif exclusively using renewable sources. The issue? This includes a ~4ct punitive tax on non renewable electricity production / kWh. Plus it doesn't factor in the state helping finance renewable projects. It's not just fossil fuels pulling the price down either, because in france where nuclear is widespread, the price is just 18ct/kWh. I do not know how the LCOE estimates deal with state or local subvention or punitive taxes, but this might be one thing distorting those estimates compared to real world figures. LCOE estimates and graphs can be made as much as you want but at the end of the day it's the actual prices that matter, and in countries with nuclear the prices tend to be lower than in ones without.
All in all, the only arguments against nuclear that you had are simply not supported by physics and reality. It will not be possible to replace nuclear in the mid term (a few decades) without a technological miracle or going back to fossil fuels.
I am, that's why i mentioned that construction times obviously won't scale exactly linearly with capacity... but i also stated that the same source gave a 1 month timeframe for a 10MW plant, so from the data i could find it is pretty linear. 1 month for 10MW vs 6 months for 50MW I don't know why it can not be parallelized more, but i would also guess that is has to do with the production of parts and warehousing them being nontrivial due to sheer size.