this honestly doesn't surprise me. i felt like it was odd that kalos was the first in the series to not see a third version or sequel and still remains that way (not counting swsh as it's still too new). there were things left untouched or unexplained, like zygarde, az's unreleased floette, az's very name itself though i might be grasping at straws. i also agree with the magearna point above. i constantly forget that it's technically a gen 7 pokemon. alolan pokemon are very tightly bound to their aesthetic and it's easy to look at a pokemon and know it was introduced in alola, imo. magearna i always think is from XY and i'm always reminded that it's 7...but it absolutely does not fit the tight motif in designs there, it much better fits in with native kalos pokemon and the region's aesthetic itself.
they seemed to leave kalos very quickly, if not too abrupt, like they wanted to be done. i wonder if we will see these games in the future? i believe kalos deserves a better version of it than XY gave us, much like sinnoh deserved better than diamond/pearl and we got that in platinum. prayer emoji. i'm not the biggest kalos fan, but given the improvements another version could have given it, that could have changed.