I don't personally see a solution other than student loan money being much harder to get.

There is so much bad research because there are too many researchers.

For myself, I think I am smart enough to have worked on a PhD in economics but not smart enough to have done anything worthwhile or to have advanced the field. I am certain I would not have. Then in the face of this massive student loan debt I would have produced junk research and try to game the system to make the investment worthwhile. The incentives are all ridiculous in the current system for most.

The idea politicians will cut student loan money in order to produce better scientific research would be a good way to optimize for losing an election.

Personally, I don't think there is a way out. If anything it probably just gets worse.

There are countries where student loans are not a thing and the science there arguably faces the same problem.

PhD is not paid by a student even in US, it's all scholarships.

Get paid to answer important questions instead of getting paid to provide sought-after results. I think that's the end-point, the "how we get there" is now the question!

Who decides what's important?

Great question. Who decides currently?

Nobody? The whole premise is that we should somehow start awarding people for working on important questions which we do not do now.

The usual critique of academia is that people are expected to publish a lot (which creates wrong incentives) and that nobody really accesses quality of the publications (which gives opportunities to cheat). At the same time there is huge PhD overproduction, which creates competition.

I don't think the problem is that people are working on wrong problems, the problem is how they work on problem of their choice and why.

I also don't think there is a simple fix to this problem.