>>33119304Alola Marowak actually works as a bipedal animal with shadow powers, though, unlike Decidueye and Oricorio. Its whole deal is that its mom is dead, so the lore of her coming back as a protective spirit is justified in its design.
I'd also like to bring up that regular Marowak likely wasn't ghost type because GF wanted ghosts in gens I and II to be rare, just like dragons. So it's kind of like that old complaint about Charizard and Gyarados being not-dragons. So it's more of an old mistake that they should have fixed ages ago if they weren't so stuck up about continuity.