As soon as Solasta comes to GoG I'm going to give it a try.
ToEE was perhaps the best game to ever capture 3.5 combat but it just didn't have story and the looting system was broken. That game really needed an EA so fans could have told them how much they hated looting and that the romances were, well, not really romances. The company was deaf to criticism even as it continually patted itself on the back for having the first gay male romance in D&D game.
Hordes of the Underdark was forgettable and I'm always surprised to find people who enjoyed it. I mean it wasn't bad but I can only vaguely remember the plot and I hated the engine itself.
So it seems a good analogue in that ToEE has the right engine but I think to compare Hordes to Bg3 is a comparison that isn't kind to BG3.
Now the game that got everything wrong was POR: Ruins of Myth Drannor.
