Windows Vista and 7 seem to be harder to skin than XP.
I think customization is not so popular anymore as it was a few years ago. This cannot be remedied.
Also there is more competition from other forums. Dunno what can make WM more attractive in comparison to the other sites. Artificial boosting of posts is no solution imho > quality before quantity.
Either that, or people are not as kyped about making skins anymore.