Not every game has to be open world. I don't mind acts; they break up a story into manageable chunks and, usually, give you an act boss as the clear goal to an area.
This allows players to know if they're over- or under-leveled for an Act, and can also be used in the narrative. Like in Diablo 2; beating Act 1 and going to Act 2 not only revealed more of the story (and thus WHY we went to Lhut Golen), but was also a time skip; it took our heroes in-world, probably weeks or months to make that trip.
In an open world, either everything has to be close together, thus making a smaller, cluttered world, or what content there is is so spread out that the world feels more empty.
So I don't have a problem with an Act-based story.
