It's funny, with some TES games I can mod them all to hell and not be bothered, but with others I want to preserve the feeling of vanilla.
My first TES game was Oblivion. I bought Morrowind for my wife in 2002, but never really played it myself. When we got Oblivion, I got svcked in. We both did. Played for a few years vanilla, and then tentatively started looking at mods. I think the first one I installed was the Shadowranger mod. Not long after that, it was Tamriel Immersion Experience. We went a little nuts with player home mods, and then got into Less Annoying Magic Experience and Better Cities --- and on and on.
To this day, our Oblivion install is modded pretty substantially, and we wouldn't think of going back to vanilla.
Morrowind, on the other hand...
I only got really into Morrowind after Skyrim came out. And while there are tons and tons and tons of mods for Morrowind by now, very few of them interest me. We do have the Code Patch and Tamriel Rebuilt - that's it. But the thing about Tamriel Rebuilt is, it's so easy to ignore. If you don't want to go to the mainland, don't. Otherwise, the game is basically vanilla. I see these amazing screenshots and videos of peoples' different Morrowind setups, but for some reason I never had the feeling of "I *need* that mod!"
And Skyrim I find quite playable unmodded. We did start adding some mods to Skyrim after a year or so, but I missed vanilla too much. Now that we have Mod Organizer, I can easily have a vanilla (or very close) install of the game and still feel free to tweak things here and there.
I wonder if others' experience is similar. Do you find some of your TES games are full of mods, while others are relatively untouched? And why do you think that is?