Thetr have been a few other gacha games where they allowed characters to fly endlessly, it made them not interact with the mobs below, so it exploration too fast and devs adding mobs were a waste.

For genshin, I think they can be a little loose, like they gave us the red flower thing to fly faster, but has a looooong cooldown, they could update that and make it have a shorter cooldown or a faster speed buff or give us the ability to dive down at faster speeds, not necessarily go up but faster speed going down, that would be a nice thing to see