Original DOOM is just strafe and your guns have no verticality.
It's also got:
- A varied pool of enemies who have different attack styles and require different approaches to defeat
- A varied pool of weapons that feel distinct and have different applications
- Great art direction in the first episode and third episode, second is debatably a bit shit-looking
- Generally good level design, moreso in the first episode than the subsequent two (let's keep it vague to avoid this becoming Sandy Peterson Hate Thread #32932)
- A soundtrack that people fondly remember
etc.
-Puzzle elements, traps, environmental hazards, which also often factor into combat.
-Various powerups (berserk pack, invisibility, invulnerability, backpack etc).
-Secrets, non-linearity, exploration/navigation challenge, large-scale diverse levels.
-A proper arsenal to manage, not a three weapon limit.
You can also mod it to have FEAR mechanics like vertical aiming, OP slo-mo and jump kicks if you want.
Guy's likely a zoomer that bases his understanding from watching some videos of 90s games.