Access to scientific discoveries is not given to those who invent them, but rather those who buy them on the market from whoever commercializes the technology (probably not the inventor). If there was a known cure for cancer then the rich will have better access to it than those who know a lot about curing cancer. Personal knowledge does nothing for you in terms of getting access to those things in a capitalist society.
Things that money can't buy are by definition outside of the capitalist system. If you are investing in knowledge in order to get access to things, you sorta have to assume that you will hold your knowledge back from the public/market, which is basically unethical.
There is obviously an issue with free-riding here where the public will gain access to "knowledge capital" that was built by others, and so people aren't incentivized to develop knowledge, and if they do they want to keep it private or at the very least charge a lot of money for it.
The solution probably isn't to have more people who are independently wealthy quit their jobs and work in science for peanuts. It's an irrational decision by them because they are unlikely to personally develop any major breakthrough, whereas by making more money they could buy access to any breakthrough made by the community. It also displaces those that aren't rich from pursuing science as a career, and the rationale given here has perverse incentives.
Better to invest in scientists generally. Even if "spray and pray" is a bad idea, surely it's better than "invest only in one person who is also the person I'm most irrationally biased towards (myself)".
Also, gaining "general-purpose knowledge capital" doesn't really help the situation. Progress is disproportionately driven by a few people that are highly knowledgeable and motivated in specific areas, along with being creative and/or lucky. Learning the basics of everything makes you a Renaissance man but isn't going to help with putting a man on the moon. Treating a cell like a capacitor is neat but probably misses a lot of details once you get into it. Digging deeply into a problem is necessary, but inherently risky as a lot of knowledge, unlike actual capital, turns out to be quite useless for practical considerations and you can't exchange it so easily.