To complete the game 80-85% of the things you will need to complete it and quests are found where? In dungeons. Aside from wondering around. If you are playing the game and doing quests to complete the game you will spend most of your time completing them in dungeons. Fact. Now I understand theres other things to do such as "chase butterflies" but to complete the majority of quests you have to enter a dungeon that looks just like allll the others texture and architectuly wise.
There are at least 7 distinct dungeon/cave architecture-types I can think of off the top of my head: Draugr crypt, Dwemer ruin, Falmer city, mine, stone cave, snow cave, and grotto. And then there are occasional combinations of those broader types.
But calling them "copy/paste" or saying that they all look alike is ridiculous. The floor plans are totally unique, and there are tons of dungeons with unique storylines. Not to mention that the designs are totally different. The end room of Ragnvald looks worlds different from the end room of Ansilvund, even though they're both crypts. And the design of both dungeons is radically different. Dwemer ruins are still immense mazes that you can spend hours exploring before you've actually uncovered everything inside.
I just don't understand how you could think the dungeons are cookie-cutter after actually playing through them.