This may seem like an odd thing to add, but personally I find it annoying to be playing in my creative world, then end up getting an Advancement for making a portal, or flying the elytra around. I mean, I'm on a Superflat Creative world. I don't need to know when I do these things. So all this would be is a toggleable button thing under Advancements that would say On or Off (or whatever).
This would also work in Survival (but I wouldn't see any good reason to disable advancements in Survival, unless you're playing an Adventure map :/ lol).
Plz. This would change literally nothing, except for people like me who notice those tiny things.