There are some exceptions to this though, e.g. Window Maker (which is what i use) feels like everything is made primarily to be used via the GUI and using a mouse (it even has a WYSIWYG global menu editor where you work with it by drag and dropping items on it instead of editing text files like you'd find in the vast majority of window managers or providing some barebones tree editor with add/remove/etc buttons like you'd find in most DEs - and AFAIK it is the only WM or DE to provide a WYSIWYG theme editor).
I find it amazing that Window Maker is both among the most powerful window managers i've used and the most convenient and graphical (FVWM is probably more powerful but it certainly isn't as convenient to configure/set up).
It looks like NeXTSTEP but it isn't really following its concepts beyond those looks. I did use NeXTSTEP for a bit some time ago, after years of using Window Maker and NeXTSTEP's window management felt very primitive in comparison.
> Nowadays it seems mostly stable, to put it on a nicer way.
Sadly it has some bugs, though it is largely external stuff (RandR support was never implemented properly and is so broken that i don't think it is even compiled in by default, mouse settings do not work since it uses some old APIs, EWMH support is buggy/incomplete and some applications that assume it is always there have issues under it), but UI-wise it is stable (in that it doesn't try to reinvent itself - a 1997 screenshot of WM looks pretty much the same as a screenshot from a current PC, aside from increased resolutions, at least unless you are on a cheap laptop :-P).
I do try to fix some bugs myself and implement features whenever i get too annoyed by something though.
I find it amazing that Window Maker is both among the most powerful window managers i've used and the most convenient and graphical (FVWM is probably more powerful but it certainly isn't as convenient to configure/set up).