I used to really like XFCE and it was my daily driver on my laptop for 6years because it was no compromises on performance type of GUI. Also worked amazing in VMs if you needed to test something and WSL on windows didn't exist.

But then they started working on GTK v3 and things started to fall apart (my experience is only from xubuntu but i think it doesn't matter). Thunar got really buggy, often crashed in random locations and it was painful to use. This one at least got fixed.

Then mousepad. It used to be really fast editor but after i switched from old xubuntu to 18.04 it feels extremly sluggish when opening lager document with syntax highlight. E.g. download html of youtube and open it in mousepad, it's unusuable.

And then the clipboard issues and large image (screenshot) killed it for me and I had to switch to KDE. It takes ~0.5-1s more to load apps like dolphin compared to thunar but at least once you load them they just work. I still hope I'll be able to come back, the zero animation GUI is appealing to me.