Loosely, jobs which pay poorly have a lot of labor supply relative to demand and jobs that pay well have a lot of demand relative to supply.

If you artificially change the price of degrees to match the expected lifetime ROI of that degree, you are decreasing the barrier to jobs that we already have too many people attempting to do and increasing the barrier to jobs we need more people to do.

Of course this analysis overlooks that some jobs are "good for society" on some metric, but no one wants to pay for them. But then the approach should be to directly incentivize those jobs eg through grants or government-funded work programs.