Thing is, DTW, procedural creation of dungeons is nothing new. Diablo did it way back when.
However your point about innovation still stands.
Innovation is something that changes the game, so to speak, and affects it for years to come. Like the joypad, when it came onto the scene with the NES, very few people actually batted an eye, but it's now the industry standard control system for all consoles.
QWERTY keyboards, the Mouse controller, all these things are innovations that we now take for granted, but literally changed the landscape of gaming.
Software speaking, one major innovation was from GTA 3: Adaptive AI. Until then every reaction done by non-player characters had to be scripted, and then looped. But GTA 3 made it so that the NPCs had a 'routine' (a rather simple loop) but whenever a threat came close, like a barreling car with a player at the wheel hell bent on racking up their hooker killing score, the immediately tried to avoid 'death' by running away from the threat. Until then, that was unheard of. But did we notice it in between our binges of Hooker Heals and Kills, and avoiding the cops as we try to jump over the chopper using the mound of cars and corpses as a ramp? Nope. But since then, people have used that sort of coding. THAT'S innovation.
But Diablo wasn't an exploration game. I do agree about everything else though.
Again to go back to how Innovation changes the way I look at games. Look at Wolfenstein or Doom. Those are games that hold up well when compared to modern Shooters but when you add how innovative they were for the time....I instantly give them both tens.
Granted before that you had Maze War and Spasism but Wolfestein and Id Software really put the FPS genre on the map.
Also , Like Random Terrain Generation , Sometimes adding a feature from another genre to your genre is innovative as hell.
If you talk to racing game fans , First Person view which FPS fans took for granted , revolutionized the way people play games like Forza and Gran Turismo. It really pushed Racing Simulators passed Arcade Racing games in recent years.
Hell , Look at going from 2D GTA to 3D. That took an already great series and pushed into the stratosphere of video game franchises.