Maybe I just didn't play long enough in-game time, but I never saw Alduin turn into a giant space dragon and physically eat the world. And I was under the impression that's what the World-Eater does. Since the world never ends if you don't progress though the main quest, is it safe to assume that Tamriel would be safer by ignoring the main quest? I mean, the entire Oblivion Crisis would never have occurred if the champion just took the Amulet of Kings to the Shivering Isles and thus kept the daedra invasion limited to Kvatch. Since there's no consequences if you ignore the "world-ending threat" in the main quest, we'd potentially save more lives by running off to chase butterflies.