The UI is poor for sure. I really hate how the BG3 UI constantly makes me search for the right buttons.

Playing a higher level Wizard with the hotbar UI will be incredibly annoying when they have a huge ever changing spell selection. And spells change places all the time and disappear into other pages. Spellcasting needs a whole separate UI element. Pillars of Eternity, Solasta, NWN2 all figured this out, it's baffling Larian sticks to such inefficient and annoying UI choice.

Temporary Actions granted by spells or other things need to all go in their own location next to other main actions. Something like Hurl Produce Flame or Activate Witch Bolt going somewhere is inexcusable.

Extra mention for the Wizard spellbook that lists all upcastable versions of spells as new spells and does a great job at hiding your actual level 2 spells when changing selection.