Possibly controversial and happy to be swayed, but to me the fundamental problem at the core of grad student oversupply is a lack of investment training.

Degrees like the sciences and mathematics (and certainly arts too) are appealing to some because they are not tied to capital (or at least, less tied to capital than say business degrees). This means there are less chances to make money, sure, but also less chances for corruption. The problem is, that isn't a complete career plan. There needs to be an "and then" that reflects the current market.

I don't have a lot of hope for universities hiring enough people to satisfy the number of current t grads. But, we definitely need innovation. Universities should be teaching students how to intelligently take risks, while not sticking their neck out too far.

Governments can help here by offering cheaper loans to young investors, or offering partial protection to investors who do. Again, happy to be swayed here.

IMO, one thing that absolutely needs to be retired is the current academic reward pattern of "better = more papers at more high impact journals with more cool positions held". It's too easy to game and too hard to be creative under. Something where the financial risk is not held ENTIRELY by the post doc is a good start.