I agree mostly on the shrines, there's little to nothing to differentiate them, and having done all of them, the amount of combat shrines and lack of variety in them is baffling. As you say, they had the enemy types, but they chose to make all the combat shrines totally identical. Bizarre.
For me BOTW is like 2 different games. There was the first 30 or so hours, when I was filled with wonder and constantly discovering things that made my jaw hit the floor, or just gave me a real sense of joy in exploring this place for myself. I think not adding waypoints automatically when you activate a tower is a genius design decision that makes the player truly LOOK and explore to find things themselves, and it also forces Nintendo to step their game up with regards to world design, and they did.
But, after a while, as stated in the OP, you realize there are only so many things to find - shrines, koroks, and enemy camps, and that's mostly it. And 9 times out of 10 when you find something really cool, it will just lead to another shrine. And most side quests are really dull and uninteresting. So the back half of my playthrough, while I was still having fun, felt a lot more like going through the motions. Overall I do think the world's a bit too big and there's too much repetition of content. But I still love the game, it just doesn't totally escape the curse of the open world game - it gets rote. It may take longer to get there, but it gets rote just the same eventually.