I've been very, very impressed with the MATE desktop. It's actually GNOME 2, carefully upgraded to GTK 3, then with a sensible set of improvements. It's available on most distributions, but the lead developer is also the lead for Ubuntu MATE.
Also I think the general idea that options == bad started in the Gnome 2 era.
not sure what you mean by 'professional', but KDE is still there chugging along (and IIRC default by suse, which is basically the 'red hat' of europe..)
Unfortunately not, no. They use GNOME as well, with some customizations: https://www.suse.com/de-de/products/desktop/features/usabili...
As much as KDE is better than GNOME in almost every way (opinion: mine), this is the one use-case that GNOME is built for. For use in centrally administered environments where the user is not really supposed to touch anything. Which is the primary use-case for SUSE Linux Enterprise Desktop (or other enterprise desktop distros, too).
openSUSE is still on KDE and I'm really hoping that SUSE doesn't violently take that over to make it their GNOME vessel. openSUSE's primary use-case is for home-users, who do need to administer their PC, and it's sort of a power user distro anyways (YaST, btrfs+Snapper, not Ubuntu), so KDE is perfect for that.
As far as I know, Gnome 2 is the last example of a Linux desktop environment that underwent professional usability testing (on regular people and power users) before shipping.
Personally, these days, I prefer minimalist WM’s and CLI administration tools for stuff like WiFi, but all the newer heavy DE’s I’ve tried have obvious (to me) usability regressions vs gnome 2.
It is funny how little usability testing is done on desktop environments these days (I also wonder if Microsoft bothered with Win 8, or if apple is with iOS these days cough podcasts cough).