It's weird, but I suspect that Act 2 and Act 3 were swapped originally. It makes more sense to have Act 2 be where you go to Baldur's Gate, learn more about your companions, resolve their personal stories, explore a large open map, and THEN move on to the big confrontation against the Absolute at the tower.
From a story perspective it's really weird how you confront the Absolute and then go on to sort of aimlessly do all that other stuff in Baldur's Gate. It makes more sense if the story acts are swapped, imo.
You can tell Act 3 had the least amount of polish put into it. Act 1 and 2 feel very carefully and intentionally designed. You can tell they planned everything out. Act 3 feels like it was rushed and they had to make a lot of compromises.
The pacing is the most obvious thing but there's also stuff like why is Gortash, the literal ruler of the city, being sworn into power in a random fort in the lower city instead of you know... the actual castle?
Act 1 is a great sandbox and the most D&D like experience as a result.
Act 2 is the strongest story and writing, much more focused and tightly built. Some cool D&D like dungeoneering/puzzles to boot.
Act 3 is what happens when you don’t leave enough time and energy to wrap it all up. It tried to be as expansive (more even) as Act 1 and they couldn’t keep up with the writing. They also should’ve done away with the entire section before you actually enter the city. Talk about a momentum killer.