These paradigms may or may not have been well thought out and useful, I'm not here to make that judgement, however what they did (particularly with Gnome 3 and windows 8) was push you to use the new way, either with no concessions at all to other ways of working, or vague promises that they would come later. This presents users with a learning curve and that's offputting when really you just want to get stuff done in pretty much the same way you did yesterday.

For me the crucial point is that Windows (pre 8 and 10), MacOS and Linux DEs like Xfce, MATE and various others don't try to push you, and do things in a fairly 'standard' way. A menu bar may have moved, some graphics look better than others, there might be a clock in a different place. But they don't force you to full screen, try to hide all the things you've done before, make choices for you on which applications to use for what, etc etc, behaviour is pretty predictable. And if it's not, you can make a few tweaks without much fuss.

So they aren't broken, but they do present a barrier to entry, and often a lack of flexibility (I'm specifically not talking about KDE as I haven't used it on over a decade).

And it's not just a DE vs WM thing. I'm fine with Gnome 2, for example - it also "just works" in that sense. And Xfce is really a DE these days, as well (I'd say that feature-wise, it's on par with earlier Gnome 2 releases now).