This is partly true, but I would also like to state things have much improved. I can vividly recall the 2000s where practically every website would look and behave differently in different browsers. I recall a lot of debugging client-state using poorly scripted PHP websites. Tooling so much more advanced and things "breaking" have moved from the user to the developer. In the jQuery days (or even before that) it was very hard to find out if everything was working as it should. Early feedback is a good thing. Understanding a framework is part of understand what you are shipping to the customer or user. Sure, it might seem more complex, but at least complexity isn't pushed down to the browsers and users.
> I can vividly recall the 2000s where practically every website would look and behave differently in different browsers.
That was a time before the web became more standardized as an app platform. Corporations like Microsoft with .NET, Sun with Java, and Adobe with Flash, were all competing take over the whole world of write-once-run-anywhere frontend apps, become the platform of choice, and lock everyone into their way of doing things. Also there was no distinction between desktop computing and mobile computing as mobile computing back then was still underdeveloped.
Now the web is the frontend platform of choice. Ostensibly the platform isn't owned by anyone but the WC3 consortium (which is good), but practically speaking, Google won since everything is WebKit now (which is worrisome). And this has not yet so far solved the problem of the web being built on an incredibly poor programming model that make everyone want to use virtual-DOM frameworks and CSS preprocessors.
Hopefully, web assembly will replace the status quo and let people develop front-end apps using better programming languages and frameworks than just the ones the compile to JavaScript.
