I'm still not completely convinced by React, and I may very well be wrong, but the same skepticism that sometimes makes me feel out of touch, also provides some sanity in this madness.
For some reason that I can't quite point out yet, Vue.js feels like the nicest one yet, though I've only played with it briefly.
Most projects I start these days tend to use React. I've looked into Vue, and liked what I saw. I also maintain a 5 year old project built with Backbone.js (by someone else) and I'd say it checks all the boxes for maintainability, stability, and testability. It has its flaws -- as any old codebase will -- but I'm happy they went with Backbone. I'd probably be saying the same thing for the other frameworks mentioned.
Its easy to point out all the flaws from our past. Much more difficult to predict how thing will be in the future. Making a choice now, even the wrong one, is almost always better than clinging to things that are known to not work.
First time I saw jQuery: Crazy easy and widely compatible, Ajax, selectors and animation - sold!
First time I saw React: Split your UI into components, write them in JavaScript (with optionally mixed in markup to make it more tolerable) - Hmm O…K….
Managing UI state can be complicated, but to me, not enough to justify the amount of complexity and abstraction added by React. If you organize your code so that only a single function can act on a specific block and emulate OO/namespaces in CSS, instead of attaching functionality to every click and overwriting stuff with !important, you'll be fine. It's not that hard, but maybe that's just me.
It's nice that the Virtual DOM is really fast (even thought I don't usually need that much speed) and that I can render it on the server (even though you can probably kiss your semantic markup good bye) and one way data binding seems a good idea, but again, I don't think it's a problem I have.
Most all web developers of that day were new to programming (experienced folk didn't take JS seriously), so naturally they did not know how to write well-designed software. The benefit of Backbone was not Backbone itself – it was the community push for thinking about code structure in general.
It even came to the point that some people reject using any frameworks or even a helper like jQuery and "take everything under their control" because they don't want to deal with "deprecated" libraries.
Meanwhile, a small development team I know keeps using Knockout.js successfully in huge projects.
Vue-router is what really got me into it. Again, it's similar to UI-router for ng1, but destroys it in simplicity and readability. I'm using their vue-webpack template to rebuild my site and it's going great.
Personally, the best thing for me is that a component gets nearly everything it needs in one file. Template, script, and scoped styling? Exactly what I've always wanted. Forgive the gushing review, but honestly, I haven't ever been this excited about a technology. Not ng1, not webpack or es2015, or [fancy new tech]. This shit just works.
The best investment that I ever did was really learning JavaScript and all it shortcomings. The problem with a longer younger colleague's at work is that they seem to learn frameworks instead. They can make cool stuff but from the moment they are in situations where for example "this" does weird stuff, they don't know why or how.
There is nothing wrong with using frameworks - I use a lot of React these days, before a lot of Backbone - but if you know enough JavaScript changing between them should not be a big deal.
The abstraction gives you hope that you won't have to worry about the low level details, it will be so easy.
But almost invariably, the abstraction breaks down or acts weird, or some low level error or limitation bubbles up, or the abstraction has horrible performance for some edge cases.
So now, where you had 1 problem - the low level thing - you have 2 problems - the low level thing, and the abstraction.
You don't have to be a uber-expert in the low level thing but it's really helpful to be comfortable with it.
I see it with ORMs - 'wow this is magic, I never have to do SQL again' - 'oh crap, a weird edge case, I have to do SQL' - 'oh crap, why is this so slow, guess I have to look at the generated SQL, and maybe hand-roll my own'.
(Not saying you shouldn't use abstractions, they can save a lot of work for the central cases where they work right.)
I remember the complex UIs I and others wrote a decade ago with jQuery, now those aren't complex at all compared to what is common now. I feel that it isn't quite fair to say that back in the day we got along fine with just jQuery.
Speaking of Backbone, I was already more or less organize my code like Backbone for a year when it came on the scene. Then there is the question, can I really program a custom framework better than an established framework?