He's a newsletter writer. You get this if you are interested in what Jared Dillian thinks, but not $1800 a year worth. If you want to see some data on the decline of college, I have a recommendation.
What is controversial is the idea that it's just signalling like Bryan fucking Caplan thinks.
I would say the fundamental issue is that the value proposition of college has become questionable. It's been a long time coming - College Inc. first aired in 2010 and that book I just recommended was published in 2013. But here - let's follow your logic:
If enrollment is decreasing, a bunch of small schools that did not provide much value to begin with will close, society will skew, tuition fees will decline or increase but the institutional rite of passage of "college" never will.
If they never provided value in the first place, what changed? If we presume "no value" then the price/value ratio has always been div by zero so why are they closing now? 'cuz they are.
To quote someone whose opinion I respect from that thread, "it was all bullshit to begin with." Yes. Certainly. But it was viable bullshit until recently.
The institutional "rite of passage of 'college'" as we know it owes a lot to the GI bill. Things have changed. The question is what they will change into.