"go over to the jdoom or risen3d communities and live with your suckish 3d models everyone seems to love"
those models are horribly edgy, blocky and amateurish: the original 2D sprites are much more detailed.
Problem with polygon rendering is that it is hyper-sensitive to surface complexity = no rough, organic surfaces. Volume graphics lets you render detailed 3D models fast and efficiently.
"its not any less great just because the times have changed."
then why dont you go back and play with your classic original pong/chess game. That game was fukcing amazing when it was first released, and omfg it still is!! :O
"When is the last time you've seen a game where you can successfully render 500 -1000 enemies on the screen at the same time?"
those aren't enemies.. they are boring static lifeless flat 2D paperdolls.
"Modern games usually require much more work to generate the same playtime Doom mods can contain."
I disagree. zdoom modders have a tendency to rip and steal sprites from games. Why`? because making new sprites is a horribly tedious and painful process because you have to painstakingly place every fucking pixel manually for every rotation and you have to single-handedly draw shadows and add lighting on the sprites. With 3D, it is much easier to make content because you can leave lighting/shadow to computer (i.e. raytracing)
makes me cringe and want to bang my head in the wall 
