i've created somewhat of a limiter in my universe to account for this..
Basically, there's a set 'threshold,' or 'store,' that a being has that can be filled with magical abilities. Investiture, although that's a cosmere term, but it's the closest thing because i don't have a name for it. Depending on the being, be it a High, Higher, or Highest being, that threshold/store changes in size and volume filled at default.
But there's a caveat: the bigger your threshold/store is, the less you can actually use it for.
Highest beings, like Wyvrns, have an insanely high threshold, as they hold Elemms, the building blocks of the universe. But, because they are bound to their Elemms, they can only act in the Intent, for lack of a better in-universe term (for now), of that Elemm.
Higher beings, which are mostly very VERY powerful High beings (think demigods, but more on the god side), have the free will of a human, and a quite high store of Investiture (again, for lack of a better term, this.)
High beings can use Investiture, but they don't have much, and it usually costs them something physically. But they also have the free will aspect.
Just putting this out there in case someone wants inspiration.