As far as Belly Drum Azumarills are concerned, this is a new, alternative way for them to sweep without needing to keep its health that high.
I don't think Incineroar has the longevity to attempt to fish for Defense drops if that's what you're implying, and Darkest Lariat can probably be come in handy against random things like Acid Armor Reuniclus or those Kee Berry Baton Pass mons or whatever.
It'd probably come down to PP comparison, and considering Darkest Lariat is pretty much the physical variant of Secret Sword (down to the 85 BP), it'd likely have just 10 PP so Crunch may win out. With that said, I wouldn't call a Dark-type physical Secret Sword a 'terrible attack'.