You've betrayed your bias in your choice of words, though: "app." And, for that matter, choosing the word "as" instead of "if."

I'm not personally building apps, and I'm certainly not building things that need to be single-page apps. I'm building websites. They may be dynamic, they may include interactive elements on the page, but they're still mostly just plain old websites with limited state to manage. Which is fine by me. I suspect, that, were it not for those social constraints I described up above, that would be fine for most websites.

One of the other problems with complexity is that it's addictive. You get a taste of it in a situation where you actually need it, and next thing you know you're afraid to go anywhere without it, because you're worried (or is it hopeful?) that you might need it again.

There is a gaping chasm between a website that needs some Vanilla JS and light interactivity, to the point where a framework like React is a necessity though. Like if all you're using React for is to pop open a side menu or render some lists, you've taken on a boatload of tooling overhead for pretty minimal gain. Performance isn't going to be the problem there, the issue is having to maintain a relatively cumbersome tooling ecosystem for the site. That's not a contrived example either, I've seen plenty of that going on.