This thread is dedicated to all those gamers who are facing DOOM or general retro-gaming nowadays (because they weren't born yet or they were still too young at the time).
I found Wolfenstein-3D and DOOM (both 1 and 2) for DOS back in 2016 and played them with keyboard and mouse from DOSBox. I didn't know about the existence of NOVERT.COM that disables Y-Axis mouse movement, so I dealt with it and have been able to complete Wolf3D at the maximum difficulty ("I Am Death Incarnate") and both DOOMs until Ultra-Violence.
In late 2017, I discovered a modern port for DOOM, Zandronum, in which you can play like it was a 2.5D game (Duke Nukem 3D or Damage Inc.) with mouse looking and disabling "auto-aim" (which definetly isn't a real auto-aiming nor a Serious Sam aimbot, I'd rather call it "auto-projectile redirecting" because it redirects bullets/rockets/plasma after shooting if you were aiming at a target which is on a higher or lower platform than your current position... or when Cacodemons/Lost Souls/Pain Elementals are flying), like it is on Serious Sam.
At "Nightmare!" mode, I've finished only Episode 1 for now.
And, back in topic, restarted DOOM 1 for DOS last week, at difficulty "Hurt Me Plenty" just to learn how to play with only the keyboard.
I'm not going to become a DOOM speedrunner: completing a level without shooting anything just sucks. My goal is to play good at "Nightmare!" mode with keyboard only.
Note: aiming with "turn left"-"turn right" is slow, but you can aim faster by using the key set for running: SHIFT. You need practice and coordination for that. I now get why people has always been saying "early 90's FPSs were the most difficult games ever" (or at least harder than modern post-2000 FPSs).