In this kind of Shounen stories you'll rarely see great details in art; even less in aesthetics things, such as clothing. Kishimoto seems to focus more on the story, and the characters, rather than on the artistic aesthetics. I am not saying that Kishimoto's art is bad, it is actually quite good, but not excellent as seen in other mangakas works.
I think that the reason behind Sasuke's post time skip outfit, would be that Kishimoto wanted him to look as a samurai. The cloths, plus the sword give Sasuke that look.