BOTW was already too big, TOTK’s sky and depths were basically a band aid solution to break the monotony
So in BOTW you had this pretty clear dichotomy between the overworld and the puzzles (Shrines). In TOTK the world feels more alive, as you have more major events outside of the four main dungeons. Besides the main quests there are other things to do, so that’s where the sky and depths come in, it’s kind of like the gameplay loop is around three tiers of grinding. You have the BOTW map that has new events + caves. In the caves you get the seeds that light things up so you can see in the depths. In the depths you get Zonaite to upgrade your battery so you can use more of the Zonai parts which you get in the sky. The Zonai parts help you nagivate the depths, you also get the flowers to make food that heals you from the gloom. See it’s like a loop, there’s also the fact that exploring the surface helps you to explore the depths and vice-versa.
That’s all fine during the first few hours but once you’re far enough, well it’s pretty apparent how most sky islands have the same layout, the depths are samey, most caves are too. So while at least it’s not just the Shrines that are samey, it’s still the same overall problem. I know the classic answer to this is that “you don’t need to do everything” but here’s the thing, it’s okay for Korok seeds and the signpost guy to be so abundant that the game doesn’t expect you to find them all, since here the point is just to provide resources to the player. However, in the case of Shrines, it’s a problem because they are handcrafted content. The game constantly distracts you and sidetracks you with shiny spots and other points of interests. When you look for a new Shrine, cave or quest, you expect them to be “one of the great ones”, one of the surprises, like Eventide was in BOTW. That’s why it’s perfectly valid to complain about huge open world games being repetitive, it’s not a “stop being a completionist” problem, it’s a pacing problem if the act of “exploring to your heart’s content” leads you to repetition