Dire Bare
Legend
You're looking at these worlds from the MtG perspective, which is understandable, but . . .Well, I definitely don't agree with Theros/Ravnica feeling more at home in the D&D Multiverse (if we are arguing it is distinct from the MTG one), unless you are scrubbing those two worlds of big chunks of their history.
In Theros' example, a big chunk of its recent history has been impacted by Elspeth Tirel. Although one could just treat her like a person who knows Planeshift and is not a Planeswalker, she definitely doesn't have much in common with D&D wizards and is much more martial focused.
Ravnica's history is much more intertwined with Planeswalkers, so much so it would simply be nonsensical for that world to be part of the D&D Multiverse and not reference the Outer Planes. Its literally a extraplanar, diverse city much like Sigil, with travelers from everywhere. It being in the D&D Multiverse but not referencing anything from it doesn't make a whit of sense.
In the D&D setting books, are planeswalkers like Elspeth and Jace even mentioned? I might need to go back and read the books again, but I don't think so.
If you take Theros, as presented in the Mythic Odysseys of Theros campaign book, how does that version of Theros fit into the D&D multiverse?
Using an expanded knowledge of the setting from the card game is a wonderful thing to do to flesh out your game, but . . . . it's not something your average D&D fan is going to be able to relate to, unless they're also into Magic.