Sure! And Chrome is superbly tested.

But HTML/CSS/JS aren't anywhere near good enough to build GUIs of any complexity by themselves, so everyone layers tons of stuff on top. And then those ... those, people have plenty of complaints about too. But if they didn't use them those complaints would migrate to the underlying framework.

I mean, Swing may have had a fragile threading model (not sure what you mean by that really), but HTML doesn't have one at all. Not great!