Agreed.
There's that, and also many of us who are refugees from Microsoft got thoroughly sick of the attitude that profligate use of system resources was quite normal.. 'just throw hardware at the problem'... uh uh, no way baby, give me fast/lean/stable choices!
On my machines I use SolusOS (Debian+Mate) & Xubuntu (Ubuntu+Xfce). Both are fast to boot & snappy to use with small memory footprints whilst still retaining all the GUI funtionality that you could need. Even on my Core i5 machine the Gnome3 & Unity Shells are noticeably slower to boot and more memory hungry.. to what end?? The ergonomics of these GTK+ 3 shells are pretty awful. I mean if you really must have type to find then just install Cardapio or Synapse.. problem solved you can feel leet..
Gtk3 also has a hidden dep on XCB - it will crash on a normal X setup, despite having been compiled without xcb. A bug is open, but with no advances.
Sorry, I haven’t checked myself (except for the lack of themes), I based this remark on the comments I read here: uses more memory, slower, lower usability (? color chooser comment), a one man project whose author thinks it needs to be redone, and I thought I read somewhere that the code/API was actually worse but I can’t find it anymore. Also the new themeing system might be “better” but we had/have plenty of great Gtk2 themes that worked very well and now we have 1) a lack of Gtk3 themes, 2) different looks for Gtk2 and Gtk3 apps, 3) need to learn a new system when the old one did the job nicely…