Funny you should mention GNUStep/WindowMaker... absolutely my favourite WM. I agree most of the rest are bloated and wonky. Gnome has removed almost all of its menus and bells and whistles and it's largely unusable now. KDE is the kitchen sink inside the kitchen sink. It's overly complicated for a DE. Sadly, there is no real focus on WM now, although last year, Window Maker Live, a Debian-based live ISO was released. It hasn't gained a real foothold among aficionados.

There was an attempt to get Window Maker back in the limelight last year. Not sure where this has gone...