It’s staggering that collaboration would be the #1 task on the core team’s roadmap. 90% plus of WordPress websites are single-owner, and for those that aren’t, WordPress is still very good about letting multiple people work on the site. The only limit is individual post or page creation. But, again, just how many users are really screaming to be able to edit posts concurrently?

As for plugin developers who create their own interfaces, the biggest offender by far is the Blocks Editor team, which has a completely non-standard interface and actively hides the dashboard. (Hint: overloading the “About WordPress” icon in the top-left corner of the block editor to exit to the dashboard is creating your own interface. With a vengance.)