I'm facepalming so hard right now....
@Rroff had a nice video showing what the path tracing engine was capable of. Need to cook dinner before having another look for it.
No idea if that's the case or not, what is "enough frames"? Enough fps is something that can vary on a game by game and user by user basis. I don't recall dlss ever needing a certain framerate to function properly.
Doom 3 is largely just stencil shadows + specular and normal maps - remove those i.e. look at the modification to make it run on Voodoo graphics it actually doesn't look great at all.
As I've got my head around some of the processes used by Quake 2 RTX I might try and recreate a bit of Doom 3 in it.