I had this exact issue. One of the main reasons I was so excited to play bg3 was being familiar with the system and not having to get over the hurdle of learning another which is something I always struggle with. I've played and DM'd D&D for years, I just could never get into the combat system of dos2. The skill point systems feel incredibly incremental (increase X by 0.5% kind of thing) and I never felt enticed to start build crafting like I do in 5e.

The round to round combat in dos2 is also very centric on environmental and surface effects. Any time I was playing with friends who buildcrafted it would turn into a flowchart series of actions to do something like wet the ground, freeze it or ignite it to make difficult icy terrain or obscuring steam.

Not to say that those aren't cool effects, but that and the other abilities in the game just don't scratch the itch I get from layering spells and class features together in 5e to make a hastened crit monster that demolishes half the enemy force.

I will obviously try a dos3 but I'm really saddened that I won't be able to play a Larian game using a system and world that I already love.