Counter-example: http://jonathanwhiting.com/games/knossu/ (Highly recommended if you have 20 minutes to spare.) The geometry of this game is unlike any I have seen so far. There is common logic with that of a Doom-like ray caster, but I'd argue not much. The time spent rewriting the generic parts of a ray caster probably pales in comparison to the specific parts of his graphics engine.

(Of course, your point stands in general. But for Jonathan Whiting in particular, I have the feeling that it may not.)