I do not disagree there to be honest. After a while the only reason i wanted to go in there was to collect unusual alchemic ingredients
For me, it was more the sigil stones. But still, the Planes of Oblivion got boring pretty quickly.
I'm not going to bash on Oblivion, because I firmly remember at least half of Morrowind being blighted land and ash storms.
There was quite a bit in the way of ash covered wastes in Vvardenfell, yes, but that's how it was supposed to be in lore too, but at the end of the day, those ash covered wastes still felt more interesting than Oblivion's lush forests to me. The forests may have looked nicer, but the wastelands were more interesting, and there was a pretty strong contrast between the Ashlands and other desolate areas and the other regions, which may be why Morrowind's landscapes felt more varied than Oblivion's. In Oblivion, when I entered into a different region of Cyrodiil, it kind of just felt like going into forests with a slightly different texture, when I crossed the mountains and went from the Ascadian Isles to Molag Amur, on the other hand, it really felt like I was entering a very different region. Admitably, such dramatic changes in environment in a game world the size of Morrowind's may not be entirely realistic, but it does help to ensure that the world feels varied enough.
Although I'd also say that there was more to what made Morrowind feel so unique than just the landscape, and I'd say that even if Skyrim has more generic fantasy environments again, it might be able to capture some of that, I guess we'll see.