Regarding the UI I agree with @El_Artista.
Natron follows the UI “standard” for node based compositing. You don’t fix what works.
Natron however needs a small style change (or refresh, call it what you want), where we fix some ugly buttons, maybe adjust some colors etc. But that’s about it (IMHO).
People that want major UI changes are probably not compositors, they usually come to Natron by mistake and assumes/want UI/UX from NLE’s, AE etc.
This is mostly a information problem, most websites etc put Natron in the motion graphics category against AE. This is at best misleading.