A hallway simulator is exactly what Doom is built for though. The whole game is corridors and rooms connected by more corridors, that's the core loop since 1993. A map that keeps you moving and funneling demons into choke points is way more fun than some giant open arena where everything just swarms you at once. If the flow works and the fights land right, who cares if it's linear? Half the best WADs ever made are basically one long tube with clever traps. Calling something a hallway sim is only an insult if the hallways are boring. Tight spaces force you to actually play smart instead of just running backwards in circles.