Part of the so called improvements in the desktop have been pruning away of choices presented to the user. Instead of 23 MUA's, ship 3. Who gets to decide which 3? Why, your distro overlords, of course. The other part consists on streamlining the distribution down to a couple of thousand packages, relegating the rest to a non-core multiverse. However, the former is the probably the major reason for the popularity: when one removes choices, and makes decisions on behalf of the end user, one can offer a slick presentation -- as long as you like the decisions made; and most people usually do not care.
Debian went the direction of choices, allowing people to tailor the distribution to their liking. This makes for more questions, and perhaps more configuration choices, and perhaps, confusion for the novice. But one is only a novice for so long, annd I am glad that the easier shoices prof erred by Debian exist.
If there is a way of creating something that is slick _and_ manages to offer the choices, I think Debian folk would be happy to hear about it.