> If you need state management, build a very complex app, etc. ... don't.
I'm not so sure you do for many sites. Take something like Reddit for example; I don't think the new SPA redesign is any better than the old template-driven app. In fact, IMHO it's worse in every way. Part of that is just a matter of design and not technical, but part of it is just "SPA hell": CPU goes to 100% on load, takes ages to load stuff, etc.
On the other hand, I find something like FastMail's web UI to be quite pleasant. So it certainly is possible, but I do think it's a lot harder to get an SPA right than it is to get a classic template-driven app right. It's also a lot more complex, which results in all sorts of problems.
I don't think jQuery is the "perfect" way to develop stuff; the lack of structure means things can get messy (we've all seen that), but I'm not convinced that React is the best answer to that (just because A is imperfect doesn't mean B is the answer, a common fallacy in these types of discussions).
I'm not quite sure what the best way is, and perhaps it already exists and I'm unaware of it, but in the meanwhile I prefer to stick with the "KISS" solution. If I look at the websites I really like using then they're all classic "progressive enhancement" ones, and not SPAs (in fact, FastMail is the only exception that I can think of).
Either way, the post was mainly intended as "vanilla JS vs. jQuery", rather than "classic JS vs. modern SPA" (although they're obviously related discussions).