The system I'm working on is shit. The devs all know it, the users all complain about it. It needs to be fixed, and not only do I seem to be the person most driven to fix it, it turns out I've been hired explicitly to replace the shittiest part of it. So that's actually pretty good, right?

Except my PO doesn't quite want me to do that yet. First, he needs me to shovel more shit onto it. Shit that's going to be the first stuff that I'll replace once I get to replace stuff, and then that stuff will be a lot easier, whereas now it would be a lot harder and too slow to be useable. But new features are more important than making this useable.

He's a nice guy, but he doesn't get technical priorities, and priorities are the primary responsibility for a PO.