Hey, I love capitalism as much as anybody. But because I do love it, and indeed am on my third company as a cofounder (with two failures) I know a lot about investor mindset. It is hard as nails -- it has to be. Nobody wants to play the lottery -- they want a plausible bet, something that might be a long shot but that is affordable and has a payoff to match the risk.
That's the problem right there. Sure, maybe some kid can repurpose old TV tubes into a positive output fusion generator in his garage or -- maybe not. In fact, I'd bet a rather lot not. Nor do I think it plausible that this same kid can build a thinking robot or map the entire human genome using nothing but ordinary household chemicals and his dad's old video camera. To solve the problems you list -- AI, genetic engineering, fusion, economically feasible interplanetary or interstellar travel (might as well dream big) one needs serious resources, some real skin in the game, and even then the odds are heavily against you.
I think I could do AI -- real AI -- on a shoestring, if by a shoestring you mean a budget of maybe a million a year for four or five years, at least, if I did nothing else and had a small staff of computer geek slaves with some mad skills. And I'm not certain I know what its value would be once I finished. My robot friend (with the intelligence, however real, of perhaps a cockroach)? We really want smart-ish but programmable and directed -- cars that can drive themselves, not cars that can be our friends.
Fusion is tantalizing, because there is this disconnect between Back to the Future movies and our imagination and the hard reality of pushing two charged nuclei within 10 to 100 fermi of one another and holding them there long enough to tunnel the rest of the way. We think "how hard can it be" -- and then when we try, we find that this is only the first of many problems. So sure, things may be changing. For one thing, my cell phone would have been a computational munition twenty years ago, and my laptop could replace a whole supercomputing center from the 80's or even the 90's. We can actually solve some pretty darned hard magnetohydrodynamic problems computationally without having to build something to try it. For another, we have lots of data from lots of things that have been tried, and that failed. Knowing what won't work helps too. IMO there is some actual hope that some of the schemes that were tried and failed can be made to work now, by solving the really hard problems that stopped them computationally first, but even if this is true one still has to take a huge risk to build the prototype and pray that it can be scaled up into production!
Lockheed-Martin can afford it. The government can afford it. Venture capitalists? Not so much. If it is going to cost $50 million (or more!) to build the prototype after $10 or 20 million just to design it and do all of the computations, you'd have to both have a very, very serious plan with a very, very high probability of success -- a proof that it should work if you build it (and if nothing nonlinear shuts you down along the way, which is sadly a risk rather difficult to estimate). So yeah, maybe it only would take 50 to 100 million dollars, at a risk so high that even if you had it all figured out and could "prove" to investors that it would/should work, they'd want to take 90% of the final company in order to pony up that much money. So sure, if it works you have a trillion dollar payday and you have a $100 billion dollar payout from that, but they have to be thinking of the 9 -- or 90 -- times that they drop $100 million into this and end up with NOTHING.
I know personally of at least three lines of approach to the fusion problem -- one conventional, one exotic, one that (I believe) nobody's thought of and that MIGHT be doable out to a prototype for a few million dollars, chump change. But try getting even chump change out of somebody that has that kind of money for a long shot, especially without telling them enough that you run the substantial risk of having your idea stolen and ending up with nothing. Any simple, cheap idea is stealable -- and the global electricity market is around 21 trillion KW-hours at 10 cents (or more!) a KW hour, making the life expectancy of somebody who enters the game without serious top cover as little as days. Two trillion dollars a year, and at least half of that money going into pockets that your invention would forthwith empty. People would place bets on who would get to you first -- and to your investors, if they weren't wealthy enough to defend themselves.
This might be the reason we don't have fusion already. But Lockheed-Martin can defend itself. So can the US government, maybe, although it is susceptible to corruption. Joe inventor in his lead-lined garage? Not so much. And lead-lined garages are actually remarkably expensive...