Short post and I don't have the math background to go into this more rigorously, but just going based off intuition.
Media platforms that create a single giant graph with tons of nodes and edges give rise to emergent dynamics that humans did not evolve to deal with. The worst voices get elevated, polarization increases, and we get phenomena like memes and virality. I think these create misaligned incentivizes.
Humans do best in strongly connected networks of up to a few hundred. The networks are then loosely connected to each other. There is high trust within each cluster because everyone knows everyone, which significantly reduces the risk of polarization, and also moderates the most... (read more)
There is an interesting book called Brain Energy by Chris Palmer which may be relevant. It takes a stab at identifying the root physiological cause of mental health problems. His hypothesis is that many psychological and mental health issues are caused by problems in energy usage and metabolism in the brain. The increased resistance to even minor tasks you describe sounds like a brain trying to conserve energy.
I don't think I buy his ideas wholesale. I'm sure there are brains with perfectly healthy metabolic health that are nonetheless wired in ways that cause a particular mental health issue.