Works for simple web apps, but for anything complex you are going to run into performance and especially UI issues. (Maybe also being limited to HTTP(S) can be an issue?)

There has been a ton of work to address all of that such as web assembly, webgl, webgpu, webworkers, websockets, http2, sse, on and on. There's a lot of web tech out there (for better or for worse). You really can make a webapp that's just as feature rich, complex and performant as a native app these days. Still tons of work to be done though, web assembly in particular needs some additional features before it can really shine.

In theory you can, but it's a mindset of "if you have a hammer, everything looks like a nail", happily pushed by Google trying to wrestle control over people's computers from Microsoft.

Yeah I agree with that. But Apple has an app store hammer, and Microsoft has a Windows hammer too. Of all the hammers, I feel Google's is the least evil of them all. They're all really bad, the state of technology today is er ... something. But at least with the web, I maintain hardware freedom and really the most freedom overall.

Is it really the least evil ?

There's a wide panoply of programming languages that can be used on Windows PCs, including specifically to make user interfaces, which are cross-platform, like Qt.