To the point where it just became "The Fonzie and Mr. and Mrs. C Show", where even Erin Moran and Scott Baio were absent due to the Joanie Loves Chachi spinoff?

Isn't that basically what Season 10 was? Barring a few guest appearances, Joanie and Chachi were not in that season, nor was Al. Obviously, there was no Richie or Ralph either, since they left after Season 7, while Potsie had basically became a background character by this point. At least Arnold returned. But yeah, for this reason, I always thought Season 10 was the weirdest season of the show.