I feel like I fully lack the words to describe what I mean here, although I’m confident in my understanding of the idea. (Which is to say, please give me charity when untangling my rambling.)

I share your sentiment and I’ve been thinking about this the past few days.
I’ve read in a few places that Musk is trying to turn twitter into a ‘one-app’ in the same way that WeChat is. The common pushback against that is that we already have that - it’s the web browser. The web browser isn’t going anywhere.
But turning the browser into a closed ecosystem that Google gets to set the standard for, harvest the data for, advertise through, and ensure that users are locked in to their version of the experience/data that they collect essentially makes Chrome the one-app.

In much the same way that google killed XMPP, Microsoft used its weight to hamstring open document formats - this seems like an effort to thread a rope around the neck of the open internet and use google’s considerable market share to close off the open internet.

Somewhat ironically, we may find ourselves in search of a ‘new, open internet’ if corporations continue to define our current internet.
Maybe we’ll call it “Web 1.0.”