It came out before Wolf3D, yes. But it came out even longer before Doom, and actually has some technical advancements over that game: fully 3D models, angled floors, swinging doors, true bridges, physics.
(Although the actual level geometry is admittedly simpler than that of Doom)
Rereading my last post, I think I came off much harsher than I meant to. There’s so much I think I would love about these games, and just a few (pretty common for RPGs of the time) quibbles that make them a challenge to get into.