I agree with one of the comments: "'Coulda been Doom++' hides how everyone wanted the leap back then." Doom++ was already well under way in the form of Ken Silverman's Build engine. Duke Nukem 3D beat Quake to market by ~6 months as I recall. A shorter timeline on the latter would have put them in direct competition with each other, damaging both. It was Carmack's job to assert technological dominance and give the in…
I don't care for the story, and I wouldn't play Doom++. Electric polar bears and some Shrub lava mule, whatever. But swimming in deep underwater ruins with full 3-axis freedom was awesome.
I couldn't play multiplayer back then. Dialup sucked and was more expensive than AI tokens. Ethernet was still rare. Lugging a CRT monitor to friend's house was a chore reserved for a once-a-year LAN party.