I recently discovered to my surprise that people are still making .wads for the classic Doom, including ones that take advantage of how much more speed and memory modern computers have to build arenas with literally thousands of enemies. I’d like to give some a try, but getting it to run on modern computers sounds very technically challenging. What recommendations can you offer?
P.S. I finally figured out why I sucked so at Doom: the game calls for extremely bold “throw yourself into the fray” tactics- the exact opposite of the strategy I tried to use of caution and picking enemies off.
try GZDoom
Also, don’t forget the Brutal Doom mod
I learned that lesson in the DOOM 2016 game. I was dying constantly in one level because I was trying to hide out in a hallway while sniping the baddies. After the 10th death, one of the load screen tips said, “Death comes to the indolent” and I went hmm… and adopted the never stop running and shooting tactic.
I suppose, my first clue should have been that the shift key slowed movement from running to walking but, the lesson was learned eventually. 
Huh, slow and cautious always worked well for me in Doom. Well, as long as I was on a difficulty where the enemies don’t respawn. And as long as I wasn’t in a straight-up fight with a Spider Mastermind or Cyberdemon (though most fights with either of those weren’t straight-up).
Another thing that astonished me to recently learn: if you have enemies packed shoulder to shoulder and you start by jumping down from a high place, you can run on top of their heads. I didn’t think Doom’s pseudo-3D (or “2 1/2 D” engine permitted this. Like the game doesn’t register them as obstacles until falls are flagged as complete, but until you’re clear it can’t do that.