The Vally put a lot of money to work on green tech / climate change back in the 2009-2012 time frame. Not much to show for it; investment has definitely slowed.
social issues: I have to agree.
Lots of B2C market-destroying investments in SF, less so down here in the valley. Sadly I don't see the flow of them stopping -- they're mostly pretty low tech and so easy for a non-tech investor to understand (or rather think they understand).
Granted, you probably want a bit less than <the time you expect to cash out the account> to figure out if your bets were correct or not and you actually have a retirement account, so it sorta makes sense, but we've gone off the deep end in the other direction, so it doesn't.
None of the things you list can be 'cured' by even a very well-funded start-up, not under any circumstances. Not even remotely close.
Venture capitalists attempt to earn a return for their investors. How do you plan to do that by ... fighting poverty? Are you going to raise $4 or $5 trillion to spend on poverty over the next 10 years? Because that's what it'll take - at a minimum, and that's just for the US. That's a task for government, not a start-up with $4 million in capital. It's an almost hilariously absurd premise you're floating. Poverty isn't a moonshot problem to be tackled or solved, we already know how to solve it. What's lacking are the necessary, gigantic resources that can only be funded by tax revenue (epic income tax increases).
Curing cancer? There is no cure for cancer. There never will be. What you actually mean is 4,972 cures for different types of cancer that require different approaches. Venture capitalists have been massively funding that effort for many decades. There will never be a cancer cure moonshot because it's impossible.
Fixing climate change? Yeah one of those venture capital firms with a trillion dollars should really solve that one. VC firms have in fact been making a dent in that for decades by funding the progress of renewable energy. You don't solve climate change with a moonshot, you make slow, incremental progress. There are no alternatives, no other scenario is possible or will occur. The notion of a moonshot for climate change is a pipe dream.
Inventing fusion power? You're lucky if you move the needle a fraction of an inch with hundreds of millions of dollars. The only entities that can make a meaningful difference in fusion are governments and people like Bill Gates that can throw a billion dollars at a problem and not sweat the losses.
Everything you're saying makes sense. It's true that venture capital structurally cannot coexist with investing in these longshot/moonshot "big problems". So maybe the problem is that tech has become too reliant, even dominated, by VC funding? Perhaps more public investment in R&D and the sciences is in order? There should be alternative funding mechanisms that don't rely on the short-term focused, pour money on ten and hope that one survives, scattershot approach of VCs?
The main point is that it is truly a shame that even though we live in an age of dumb money thanks to the Fed and ZIRP, and a lack of places to put that money into, the natural response is to invest in yet another food delivery/ridesharing app, rather than the stereotypical big problems.
Perhaps the problem is that VCs have too much money to begin with?