I disagree with the question's premise. Most of the "terrible" referenced is likely in code outside WP's core. There's cruft in in core; rectifying that's an on

I disagree with the question's premise. Most of the "terrible" referenced is likely in code outside WP's core. There's cruft in in core; rectifying that's an ongoing process. With CMS tech, I've seen even smart developers consistently underestimate the difficulty and time involved in building subsystems like user access controls, document revisioning, media asset handling. There's decent separation of logic, content, and presentation. There's a huge community of users and developers. And the principals are serious about Free Software. None of these things are easily replicable.