So I might make a seperate thread but it does certainly not hurt to add to this list so Larian have some overview.
D&D Rulebook
Great Weapon Master (GWM): Please please stick to the 5e rules and make it optional to use. GWM's efficiency is always dependent on the characters to-hit modifier and the enemies AC. Especially in early levels a forced -5 on hit is really hurting
User Interface
I was not able to find a list of taken Feats e.g. GWM in the character sheet
Skill Proficiencies should be displayed in a list and on hovering them the source e.g Class, Feat or Race should be shown
The Sort Inventory button should be placed near the inventories and made more prominent
Combat Dice Rolls should be visible at all times
Companions
Please let us adjust the stat blocks of companions when we first recruit them. I do not want to have a Fighter with a rather random 13 DEX and 11 INT if almost all enemy stat blocks are optimized for their purpose
Battle Encounters and their Balancing
Surfaces should be much less because it does not fit into the 5e Rulebook, especialls Cantrips creating surfaces that deal damage even though the cantrip missed
High Ground should be less useful. Right now it is basically a must to straight rush to the high ground to get boni on to hit
Amount of Enemies per Encounter should be reduced. Action Economy is real big deal in 5e and having 10 enemies with 10 actions versus the party with 4 actions is making fights really difficult if you do not cheese them
Weapon Alloys (dunno what it is called in English. I talk about the poisons and magic arrows) should be much less frequent since they are able to boost the damage immensely. Same goes for spell scrolls that you find around every corner
Amount of Spells/Grenades on Enemies is way too high. If every enemy mob can either AOE my party or use spells then the current amount of enemies per encounter is just way too high
Forcing the players to long rest after every fight because you had to use almost all spell slots for a fight is really tedious since it involves loading into the camp and going to sleep so often
AOE abilities other than those from 5e should be avoided. Why even play a Fighter or Ranger that have to rely on skills or Spells to deal AOE damage when one can use grenades or other tools to deal way more damage to more enemies
Initiative is sometimes really strange where one member of the party gets 2 turns before another member gets their first turn
Jump should be no free Disengage or at leat take up an Action in order to balance it
Fix the stat blocks of enemies. Some of these are so overtuned for their intended level.
Performance Issues
Game taking sometimes up to 2 seconds to open a loot container is really annoying
Game taking much time to load in objects and textures after a rather long loading screen makes no sense to me
Quality of Life Changes
Please let Companions automatically jump when the currently controlled character jumps because it is tedious to do this 4 times and sometimes the AI will let the other companions walk to the spot where you jumped if there is a way to walk there
Improve the pathfinding on the maps. If there is a clear path to a door and I click the door I do not want to be greeted with the "You can only reach this spot using Jump" message
Probably some of the stuff is already mentioned in other posts but I do not want to read every single entry (Plus stating it in multiple posts shows how important the point is)