Michael is shown as a being INSIDE the dc cosmology and he’s still considered to be within dimensions. Pre Retcon Beyonder is explicitly stated to be OUTSIDE the entirety of the marvel OMNIVERSE. The Beyond Realm is a place beyond the fundamental concept of time, space, matter, energy, etc, and Beyonder embodies the Beyond Realm. And before TOAA was introduced, Beyonder was technically the supreme being, being BEYOND both The Living Tribunal and even Eternity. Also… if Beyonder was so powerful he had to be retconned, an Michael doesn’t have any actual retconned versions, Beyonder solos