@honoriscreed You are correct in the fact that we have nothing to do with the quality of third-party themes.
As far as the UI, we're aware there's room for improvement. There's redesigns for various aspects of the UI which will eventually see the light of day. No guarantee you'll like those either. Bear in mind, the UI is completely user-stylable, so you can pretty much redesign it to look however you want.
Stylus is maintained by a small group of former Stylish users who forked the original project when it was converted into spyware. We work on it in our spare time, and mainly focus on fixing bugs, improving existing functionality, and occasionally adding new features.