Maybe the oversupply could be addressed by encouraging students to wait until their 50s to pursue PhDs and research work, i.e. shrinking the supply by reducing the number of years between getting a degree and retirement. With more students coming from a position of financial stability after decades of work, more of them would be able to decline exploitative opportunities as well.

Moreover a later start would also mitigate the tension between starting a family and pursuing academic interests, since the offspring would be out of the house (or well on the way) by the time the academic career begins.