Sometimes Ciro Santilli says half jokingly that user interface does not matter.
This software circa 2010-2020 makes that joke not be funny.
How can a UI feel so clunky!
The most aggravating thing is that it is not immediately obvious why it feels so bad.
This is generally good, especially compared to how crappy Evince, the default Ubuntu one, has been around 2014-2020.