Ezra being missing is enough explanation for me on his front, but I agree that “Ahsoka isn’t technically a Jedi” is a load of horseshit and her not helping Luke and co. in the OT requires a satisfactory explanation on its own.
Letting her die in the S2 finale would have been perfect, but no, Filoni just can’t bring himself to kill her even though it’s the logical thing to do…