I'm glad the new Zelda isn't on Xbox or Playstation. If it was, it would have an achievement for finding everything. Instead, there's no way (and barely any reason) to tell whether you've found everything. To determine if you've scoured a region of everything it has to offer. And it's a stronger game for that.
The 100% goal is the pursuit of a "complete" playthrough of a game, which is treated as synonymous with perfect. The allure of perfection drives us to play a game far longer than our own interest in it, running our enjoyment of it into the ground. I think Zelda's avoidance of telling you just how much is in a region (and complete lack of missions about 100%ing anything) is deliberate. Without an artificial goal compelling you to complete everything, you just do stuff until you're satisfied and then you move on. Zelda doesn't overstay its welcome.