It's not just that. Most of what makes Doom a good game has to do with the levels design, the secrets, the good balance of weapons vs enemies, and so on. Doom is still a very good game to play nowadays, much more than the boring and horrible Doom 3 for example (or even Rage for that matter).
You can convince yourself of the importance of level design by comparing the Doom mods vs the original game. Same mechanics, but the level design isn't as good and it changes everything.
Even some Doom clones are fun to play through today. I deeply enjoy Duke Nukem 3D and Blood, the latter of which imho, doesn't get nearly as much recognition as it deserves.
You can convince yourself of the importance of level design by comparing the Doom mods vs the original game. Same mechanics, but the level design isn't as good and it changes everything.