I don't intend to say the author is "bad", I'm just trying to follow up on this reasoning:

I learned the tools I was told to learn. I watched the right talks. I followed the right people. I can point at a neat little row of experiences and say: I played by the rules you told me about.

The rules are, do well at your internship, and you'll probably get a job offer.

The author also seems to be saying that they are getting interviews, but no job offers. ("The interview loops still exist, recruiters still send polite rejections.") Another rule is, if you do well at interviews, you will get a job offer.

So, without putting any value judgment on anyone, this is what's happening. The author isn't doing well enough on internships and interviews.

So my advice is not "just apply to more places", but to do that and also practice programming in order to interview better.

I have to agree with you. Companies don’t waste time on interviews if they don’t really want to hire. And if they didn’t hire him, maybe is because was not a good fit, and probably hired someone else. So the job was probably filled — by someone more competent?

Companies do waste time on interviews when they don't really want to hire, for numerous reasons. 1) To test the labor wage pricing of the market, 2) for legal or tax or optics reasons (in order to get cheaper H1B labor you have to have been trying to hire domestically for the role), 3) to placate someone internal (cheaper to perpetually pretend to be hiring than to actually hire).

I'd bet there are others. It's easy to imagine that "companies don't waste time" but companies waste time and money all the time. The bigger the company, the more waste.

Yes, but from the hiring effort what you said maybe is 10-25%. Any reason for this to increase in the last years to justify so many rejections? TBH I know many people that changes jobs in last 24 months just fine.