Well, I do not agree at all.
Morrowind's themes fitted perfectly with the environment and if you placed the Oblivion's music in the environment, it did not fit at all.
I think Morrowind's combined atmosphere was just perfect, and it is just our preferences.
Oblivion's melodies suited the more action based theme of the Oblivion, and it's newer engine let us have separate dungeon music as well, so there.
I loved the moody and dreamy atmosphere of Morrowind much more than Oblivion's action based tone.
Don't fit? Oblivion had music separated into town, explore, and dungeon themes and fit very well with their respective areas and Cyrodiil's generally peaceful atmosphere, in my opinion. Oblivion's in-game soundtrack wasn't more action-based than Morrowind's... not at all... NOT AT ALL. Both games had peaceful, well, peaceful music and both had action-based battle music. Where you even got that Oblivion's in-game themes were action-based... I do not know:
http://www.youtube.com/watch?v=bHGgBugeyHI
http://www.youtube.com/watch?v=6LN6qwMBFwA&feature=related
http://www.youtube.com/watch?v=nYFmH5Sp2Ao&feature=related
http://www.youtube.com/watch?v=G02StZzQqd4&feature=related
http://www.youtube.com/watch?v=3dme_mwnNjI&feature=related
http://www.youtube.com/watch?v=GIs2E36nzMI&feature=related
http://www.youtube.com/watch?v=wJzzUKgjsbw&feature=related
http://www.youtube.com/watch?v=8hnskP7fg1E&feature=related
http://www.youtube.com/watch?v=F3AhRH8keAU&feature=related
http://www.youtube.com/watch?v=ICn1O9uzd1g&feature=related
http://www.youtube.com/watch?v=1gszfeS2B-U&feature=related
Oblivion's main theme is action-based, but the in-game soundtrack just doesn't fit that description no matter how you look at it. In addition to that, regionalized music is actually pretty relevant and, considering Daggerfall is six years older than Morrowind and had even more regionalized music than Oblivion, technology has nothing to do with it. By all means, prefer Morrowind's soundtracks, but at the very least, make sure you actually remember what Oblivion's sounded like.