DOOM 3's main issue is the same issue 2016 and Eternal have: no community-created content. Like, I don't think a lot of people really replay the classic campaigns -that- often, maybe every now and then for nostalgia's sake. And that's true for 3, 2016, and Eternal: you beat them once on the top difficulty (barring 3, whose nightmare mode is... weird), then you take a break and maybe return to them in 5 or 6 years or something. The content is always the same, never changes, so you need to forget before you go back to it. Even if they released level creation tools, with just how complex the engines are compared to classic, I don't think there'd be anywhere near the amount of content.
DOOM 3 is just such an interesting item, though. The engine was light-years ahead of its time, and it's just capable of so much more than the game's actual level design and enemy encounters took advantage of. You could remake the game with the same engine, take advantage of modern awareness of engaging level design and better verisimilitude (less dead-end hallways that were clearly just monster closets), and have a real banger on your hands. You might want to hire more than 3 voice actors, though - that's the most jarring thing about that game when you go back and play it.