I’m under the opinion that Haiku’s UI could definitely use a refresh.
There are too few devs lately though to do a complete revamp though. The goal for Haiku R1 has always been a “BeOS replacement”. R2 is generally where we (as in the community) planned to make UI improvements.
We have been dragging our heels though on R1 due to resource shortages.
My personal favorite mockup is Haiku UI Mockup The exact details have aged a bit since 2009, but it shows that our UI can be improved while keeping our current timeless UX.
If you want something better, i’d recommend writing it. Nobody is going to outright reject a decent attempt at UI improvement. Worst case if nobody else agrees… it becomes something outside of Haiku you can install.