I suspect in the 80s the job market was acting like having a degree implied a graduate was in the top 5% of humans by ability. Now it'll be more like top 33%. That is getting dangerously close to signalling that someone has a warm body as opposed to an unusually bright mind.

I suspect that is the driver behind a lot of the points you make - it isn't possible for universities to maintain a little culture of intellectual curiosity off on the side when double-digit percentages of the population are moving through them.