It shares the trait of every QT app the ux is horrible.

I do agree that most Qt apps don't put much attention on UX - but I tried to with my Qt app: https://get-notes.com

I've been trying to use Kdenlive for years now, and everyone raves about how great it is.

I don't know what they're doing with it, because it seems to lack even the most basic editing functionality.

yep and it crashes all the time, at least for me.