I wish they had a good system for setting up and managing user roles.
A lot of alternatives do individual X, Y, or Z functions better than WP. None I've seen have achieved a reasonable fraction (say, >40-70%) of the extremely broad set of aggregate requirements the entire developer, designer, and user communities would need to commit to a WP replacement.
Unfortunately, the can of worms that opens up in Wordpress is one of the worst things about it. Every plugin and theme is essentially its own ad-hoc web application running with global privileges.