I think a lot of it comes down to nomenclature and tradition more than "lack of applicable ideas,"
When console gaming was in it's genesis, you had, what? Arcade games, sports games, side scrollers and what's today most closely associated with RPGs. That is, a large in scope, grand adventure, from top down perspective that is globe trotting and world affecting. The common naming conventions that we've kind of forgotten the shorthand to, and associate the terms more with what they mean to game design than what they mean to their own definition play a huge part in this. The Legend of Zelda, the original Famicom title, is the earliest my unlearned ass can recall terms like "overworld," and "dungeon," being used as gaming phrases. Overworld referring to the bright, sunny, wide open realm. But of course, to have an overworld implies the presence of an "underworld," and I think that's the hump current devs have trouble overcoming.
If you look at anything I'm RPG gaming under a binary lense like that (and let's face it, most do) anything that takes place in a building or structure and contains enemies, traps and bosses will be a dungeon, and anything opposing that will be an overworld. I can't speak much of Roguelike games, having only barely passing knowledge of The Binding of Isaac, Returnal, and that weird tower thing in Final Fantasy X-2, but I think if we look for alternatives to the classic gameplay loop of RPGs in general, we can find a few examples in franchises that ironically have kind of codified the "old ways,"
The Legend of Zelda: Skyward Sword
This game HAD temples, but the way the overworld (The Surface) was built in game design terms essentially had these temples littered in three massive segmented overworld sections so thick with puzzles and backtracking and enemies that they were essentially large dungeons with smaller ones inside of them. The idea of "everything is a dungeon, but some of it has overworld wallpaper," was an interesting take, but it could wear you out over time.
Final Fantasy XIII
The hallway simulator. You follow a tunnel for 20-30 hours until you pop out the other side in a large bowl of open ended decision making before being squeezed back in for the finale. This game kind of used the "everything is a dungeon," styling of earlier, but without even the quest for upgrades or heart pieces. It was just a straight up gauntlet. Like the Uncharted of Final Fantasy games. A straight path with a few setpieces and distractions.
The Legend of Zelda: The Breath of the Wild
Haven't actually played this myself, yet, but from all the research and gameplay I've sat in on, it's the opposite approach Skyward Sword took. Everything is the overworld. There are small puzzle boxes of shrines or what have you that litter in dungeon qualities, but the vast majority of gameplay is taking an old formula and putting it in a new place.
Each of those examples has fans and detractors. Clearly, you can definitely do OTHER things. Hell, Elden Ring seems like a pretty good departure from Souls games in terms of that. It's just a question of how well devs can integrate enough elements of their genre to be recognizable into a new format without irrevocably changing it into a different type of game.
