Gnome 2 and KDE 3 were pretty good. Then both shells lost their way. Why do they try to be a bad clone of macOS rather than keep being a Win98 on steriods (KDE 3) or a more simple shell for normal users (Gnome 2).
In my opinion, Gnome 3 is amongst the best desktop shells I've ever used. It's focus on simplicity in the base, while including extensibility using, well, extensions is unparalleled. I like that I can choose my own complexity and features without resorting to editing config files or hacky black magic. It's only marred by a subjective lack of quality, quantity and consistency in applications, as is the entire Linux/Unix desktop.
So to each their own. I also think KDE 4/5 are much nicer than KDE3.
Try and switch to Gnome 2 / MATE for a little bit and see the drastic improvements in responsiveness, though. That's what kills gnome 3 for me. Even on a nice high spec machine I still end up conscious of the UI latency, and that's really not a good position to be in. The UI needs to get out of the way, and a key part of that is being fast.
I don't use anything GTK2 based any more as the lack of smooth scrolling support is really jarring for me, despite the fact that I still like Gnome2's basic design.
I think the shell being written in javascript was a double-edged sword. The extensibility is really cool, but the performance is borderline unacceptable.
It makes much more sense for them take a better base to start with, and then rally developer effort to make it more customizable/productive, than take a project with a huge featureset but very fragile and unstable.
I completely agree with this. Back in the Gnome 2 days I was very happy using Ubuntu. As someone who has used MS Windows for a couple of decades, the way the Gnome 3 desktop switched to Mac-style interface, without any option to change back really irritated me. I don't think I'm alone, I think there are a lot of people who have used Windows who were alienated by the gnome changes and gnome devs preference for creating shiny new things over having things that worked and had few bugs.
I have tried to customise gnome in the past and it didn't have sufficient customisibility to have a windows-style bar at the bottom with apps, start menu and clock and also menus on the apps instead of on a common bar. I did try Mate but the distro wasn't up to the quality of what it was trying to replace. This was probably 3 years ago now though.
Making the file manager like the Mac finder was pretty annoying too (I think that was KDE 4 though). So much functionality went away when they did that.