When it comes to hotbars, I think of Final Fantasy 14. You can have like 10 hotbars if you want, something like that, and you can customize them however you want. All buttons on the hotbars and they are all the same size and squares, etc. 12 slots per hotbar. And then, you can place them wherever you want on the screen. Very bottom, on the sides, etc. Get's the entire UI out of your way.
Sounds great, at first. However, the more abilities you can do, the more those hotbars become SUPER confusing. Now, when I play the game, I have my core 6 or 7 moves and when I have to do others I have to try to remember where I put them and what the buttons looked like. I've got real time monsters killing my companions and I'm trying to find Raise spell and Swiftcast so I can just bring 1 back to life. VERY frustrating when you've forgotten where you put it.
So I must agree with Tuco in that the thing I LOVE about Solasta's UI isn't its appearance but the fact that everything is exactly where I want it to be every time. Once I get familiar with the UI in the first 10 minutes of gameplay, I know where to find whatever I'm looking for every time. Need a spell? Click spell and pull up your spell's menu. Want to use a Special Ability like Action Surge? Click Powers and there's a small menu of all my fighter's special abilities. Do I want to know what bonus actions I can do? Look to the right on the main UI. Actions on the left, Bonus on the right. All laid out for you. No hunting. No trying to remember what the button looks like. Nothing. Well labeled and in the same spot constantly.
And do you want to use items? Click Item button. Menu of usable items - in Solasta you get like 1 and maybe if you've equipped some magic item like the crown you might get 2, but it could work just as easily for BG3. They even have something like that for Throw already.
I just don't get the love for all these hotbar buttons. I know... it's probably a ME thing, but I definitely would love a simpler and more consistant UI.