The points at which the game transition between acts seem a bit arbitrary (mainly for Act I to Act II), and I don’t see a narrative or mechanical reason to lock us out of previous maps and quests. As far as I remember, previous Baldur’s Gate games didn’t have this kind of points of no return. Why do you think they did it? Do you like it?
In act 1, if you don’t resolve the druid/goblin/tiefling dispute, and iirc the burning house before reaching act 2, it resolves itself. If you did nothing the grove’s ritual finishes, if you killed the druids the goblins invade and kill everyone, and the other options don’t matter since you would resolve the quest, oh and karlach’s personal quest too, if you don’t do it she leaves.