That is not exactly correct. FVWM is pretty much a desktop writing framework. It provides you with directives to write your own desktop.
FVWM of today supports many things that 1996 FVWM didn't.
I personally find FVWM too low-level and dumb for my taste. I have to spend too much time configuring it to do what I actually want (as opposed to what I told it). E.g. I never managed to get it to do the proper desktop movement IceWM has (but I'm also a bit lazy).