In my opinion the only real thing, that wordpress does not have on this own, is a core implemented ACP (like joomla has).
I know there are many plugins, that try to add this feature, but it's not the same, as wp would includes it core.
For example many plugin authors will add compatibility to their plugin to work with the wp access manager. So they can set, if user group xy can comment on a post or can access a certain page.
So the admin can create/manage user groups and set right, the group has.
What do you guys think?