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.
Well, that was what I compared just because those two games came out in the same year, like Solasta and BG3. There was nothing else that came out at the same time as ToEE to compare it to.
But I did really like Hordes of the Underdark. I mean, it's no Planescape: Torment or Mask of the Betrayer, but it was worlds better than the Neverwinter Nights 1 original campaign.
Edit: The other thing that was dope about HotU was that it was one of the very, very few D&D video game campaigns that started at a high level, instead of being level 1 scrubs AGAIN.