Many universities did have forced retirement policies for professors above a certain age. I don't think those policies are common anymore. I'm not sure how much

Many universities did have forced retirement policies for professors above a certain age. I don't think those policies are common anymore. I'm not sure how much they would help anyway. A few more jobs would open up, but not nearly enough. It would be a drop in the bucket. The bottom line is that there are way too many graduates for the size of the academic job market, and even if the number of newly minted PhDs dropped by half, there would still be too many. In some fields, the number of new PhDs could drop nearly to zero before it made sense to get one.