Yonko saga had good ups, horrendous downs.
But even then there's still stuff like Fishman Island and Punk Hazard.
FMI was basically the other side of the Fishman/Racism story with Arlong Park. It was purely to establish SHs as "Powerful" now.
Punk Hazard was good, we got to see Law, Vergo, Smoker, Monet, Doflamingo, Aokiji in Post TS. It isn't a standalone arc, it was meant to be the starting point for Dressrosa.
Then came the Yonko Saga which trashed the Post TS.