It's trends in the air. Morrowind was more original, it came from the designers minds, in their attempt to make something mind-boggling and impressive. When Oblivion was around the corner, everyone had watched LOTR in the cinema, so Oblivion was much more lotr-i-fied, horses, European medieval, glittery fairy-tale exteriors, etc. Nowadays, there is Game of Thrones. Drab, gray, gritty and realistic. Everyone masturbates to it, including me "Gnnnhhhh so gritty. Gnnnnhhh he mentioned people shitting themselves during battles, how observant hhhrnnn" so naturally, Skyrim jumped on that trend, drab, gray, and if they could, woulda shown people pooping themselves while fighting.