Turn-based is a factor, but mostly it was the overall vibe. The art style isn't compatible with me. There's a plasticky/MMORPG/mobile-game quality to it. The use of color is horrid. I didn't care for the itemization, combat mechanics, NPCs, or writing. The main story was dull. Some side quests were good. I find that I prefer, for this type of game, a fixed camera without rotation or close-up zoom, so as to leave some things to the imagination.
I went into BG2 blind without having played BG1, having bought the game discs from my friend who told me the whole game was in a dungeon. Was hooked already by the second floor, but then you walk out the shaft into the daylight of the Promenade, and the music starts swaying, and there's a whole exotic city to explore. I don't think anything will ever beat that for me.