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?
They do give you hints with some of them - I did a long rest and everyone was telling me we needed to hurry or the dude trapped under rubble was going to die. I thought that was a good way to handle it.
Exactly, all the time critical events I encountered had NPCs clearly indicating it’s a time sensitive issue.