Continuing the discussion from Youtube-dl GUI finished:
What makes it ugly? The buttons? I find that if the buttons are better it looks fine. 
the buttons are defined by the OS AFAIK, it's more the general options, widget outlines, coloring and spacing (it's cramped) that I dislike.
Qt5 and GTK3 have a lot more to offer.
oh yeah, I forgot. the linux define looks like win95 tho.
I'll try out qt. Seems complicated tho.
Use "pyside2" to be able to use python like code as Qt5 is C# oriented.
That way it'll all come easier and on top, like I mentioned before: "QtCreator" is excelent, just requires getting used to "signals and slots" as a means to have a GUI communicate with it's surroundings.
It really is very well thought out. 