Im in act 3 and only encountered the “you’re underleveled” message once at that same point. I havent scoured the areas for everything nor speed run the main story. I think act 1 is tight like you said, but it seems to be much looser as you progress.
I second ‘The Witness’. Its a great game and the puzzles get very interesting as you progress and begin to understand the world you have been thrown into.