Simply put, no one with the necessary skills has come forward and demonstrated the willingness to do the work. No programmer I’ve ever met enjoys wrestling with other people’s crufty old code. It isn’t fun, it isn’t creative, and it’s often an exercise in, “What the unholy fsck was whoever wrote this thinking, and where did I put the ‘Bang head here’ mousepad?” So getting volunteers to mop out the bilges only happens when someone really wants to keep a particular piece of software working. It’s actually more difficult than getting people to contribute to a new project.
So getting rid of X’s accumulated legacy cruft isn’t impossible, but I suspect someone would need to set up the “Clean up X” foundation and offer money for it to actually happen. (I’m no happier about that than you, by the way.)