Earlier quoted context omitted.
Except that SPA frameworks are designed to complicate things, not to make them easier to understand. And SPA framework developers are crazy expensive, mor expensive than seasoned C++ systems programmers. (The two facts are probably linked.)
Have you ever developed a complicated front-end system? Not using a vue/react style framework would be ludicrous (ie, building something like Facebook Ads UI or Google Analytics UI). I find it super bizarre you say "complicate things" when they do 100% the opposite. I would love to understand what you would use if you were tasked with building FB Ads manager interface: https://disruptiveadvertising.com/static/61a4440…
They're way, way overengineered for the very limited use cases they're designed for.
If you're going to ditch the browser API's and re-write the world in Javascript, why not take into consideration all of the history of GUI development and do it right? I.e., make a real layout engine, proper widget hierarchies, real encapsulation, etc.
Instead there's some sort of frankenstein in-between state where you've ditched all the benefits of native browser API's but haven't arrived anywhere that's a true paradigm shift.
TL;DR - yeah, they make some things easier to reason about, but for any sort of non-standard webapp you'll still need to write an equivalent mountain of hacks and framework adaptors.