I don't know how many interviews with Brandon you've seen/read, but he's always said that he intended the Cosmere books to become part of a more unified narrative over time. You are, of course, not obligated to like it. I think the Cosmere project is already over-ambitious, honestly, but that's what Brandon is doing. I think he consciously decided to have an incredibly broad scope and see if he could pull it off. (That last sentence is pure speculation.)