Honestly the fact that it was based on D&D had very little to do with what made BG3 great for me. I switched to Pathfinder 2e in January of last year, and playing through BG3, I was frequently thinking about how awful the 5e system was for that sort of game compared to the Pathfinder 2e system. Especially when it comes to character creation. So many of the feats from the core rules are utter trash, so many of the class features are completely useless, to the point that they needed to significantly buff many mechanics just to make some of the choices not be completely worthless.