I think this is the crux of it. All the objections to WordPress are from a developer's point of view. But when you scoot around to the user's side of the table, all of those issues are invisible. WordPress dominates because WordPress addresses its users' needs well enough that it's really, really hard to be so much better that you can overcome the network effect. In order to beat WordPress, you need not just a better technical foundation or some whizbang design — you need something that makes it so much more attractive that people who aren't developing for the platform say, "You know, this is worth the extra effort compared to WordPress."