True, but on the other hand, maybe only a very small subset of people should be doing a PhD.

That's what used to be thought about any school at all, then about high school diplomas then about a university diploma. Each time it was decided that by expanding the number of people they would get uplifted to a better standard of life, a higher class etc. But social status is relative and mostly zero-sum, so the value of a diploma simply goes down when everyone has one. Chasing credentials without actual value contributions cannot cash out in anything real.