Hi. I have a fundamental understanding of what people are building. Most of it's overcomplicated and the "web app or not?" decision's very often made due to hype, résumé padding, or making a project look more impressive to other internal folks. Some of it's justifiable as a "webapp" is truly a decent choice but still usually performs worse than is reasonable, indicating overcomplication under the hood—look at various Google "webapp"s performance dropping steadily over the years as features remain similar or drop off, and that's not even comparing them to older non-webapp incarnations which are universally much snappier (though usually missing some features, to be fair).
I think a lot of the cost has to do with the underlying tech not really being that great for what it's being made to do, in concert with everyone feeling the need to try to be special in even the tinies little looks and behaviors. It's also where a lot of the audience is so will tend to experience oddities like this more exaggeratedly than other fields.
Your manager or project owner or whoever says "we want a webapp" are you gonna stick your neck out and argue against it? "But it's what google's doing", "but Gartner", but whatever. It's cheaper! OK, sure, here's my bill. It's absolutely follow-the-leader behavior, damn the cliff. And it works well enough that it does get the job done, eventually. It's just not necessarily doing the users any favors, or your bottom line.
Decision makers do strange stuff all the time because they think it makes them look better—and, to the extent and in the way they expect it to, they are probably right more often than not. This is just one example. Whole world's run by guesswork, personal quirks of taste or incentive, and blame-avoidance (follow the trends), more than anything else, from what I've seen. It's just people, running around doing funny people stuff, hoping no-one calls their bluff.
[EDIT] actually, look at Java Applets and, more so, Flash. Folks hated the way lots of those were used, but the worst and least-justifiable uses of them happened anyway, for a long time, because managers wanted the bling. That was, seriously, it. And developers went "oh sweet I can add Flash 5 and Actionscript to my résumé, I've been wanting to play with that". That's exactly what happened then. This is exactly the same thing, just much bigger. And in both cases sometimes the tech was used well.
The question is: what are you going to argue for instead? Not using the web at all is a non-starter, especially in the retail space where you'd get killed by a web-based competitor.
I don't know what your experience is, but historically my bosses haven't given half of a damn what tech stack I use. They care that I deliver on what I promise. Hypothetically, I could still be using PHP/HTML/jQuery but there are a great many reasons I don't and not one of them has to do with padding my resume.
[EDIT] incidentally I notice you keep arguing against things I've not actually written.
> ...improve UX, performance, maintainability, and development cost.
I don't buy it at all. As mentioned, I've done both professionally and there are reasons I keep picking React (or a hybrid ala Next) that don't involve a bigger paycheck or "peacocking".
> It's because I've been trying very hard to understand what your contention is.
I appreciate it. Seriously!
Bootcamps are something that grows out of this desire to pad your resume with newer tech.
I build SPAs as part of my job. Good SPAs do not break the back button. Insisting they do is silly.
This opinion invalidates the rest of your post. If you lack a fundamental understanding what people are building obviously it seems overcomplicated.