We have terrible intro and radio chatter. We have boring mc'boringface MARINES. We have weapons being dull, grey and ugly hit-scans. Only hyperblaster and railgun have interesting projectiles' design. We have terrible hand grenades. We have giant disparity in gameplay between SP and MP. We have almost entire enemy roster being occupied by enemy a little bit ᴄ ʏ ʙ ᴇ ʀ MARINES with mostly hit-scan weapons. We have enemies which just refuse to be dead. When he falls on the floor, you continue to run forward, only to get shot by a supposedly dead mob in the back. There was similar problem in the Duke Nukem 3D, but there only one type of enemies did that. We have unending generic intestine brown corridors, with uninspired level-design. And of course, in a linear shooter, we have an occasional hub, which requires you to backtrack and return to the previous level through a loading screen. Like, i'm not entirely against such thin, but player doesn't have to check a separate menu, to see what to do. There always must be a clear goal. Doom always contained backtracking in borders of one level and had a map. So there was a clear current goal and no finality of a loading scree. But here you have to load a new level and then return the same way you left. Usually, when games want you to return someplace, you do it accidentally by going forward and discovering a new short-cut. Some (bad) games are openly declare to you that you need to do that. But this is almost on par with the F1 in the Postal. But there, i suspect, it was intentionally bad design, not accidental.
When i've finished Unreal i didn't like it, because i was comparing it to the MP part of Quake 2. But now, when i have the full context, i kind of want to check it out again and see if it's actually better than Quake 2 SP.