Because Rosario is a boring opponent, it's more or less certain Mashiba will win, we've been getting chapters with very few pages for a while now and this is at most Morikawa wrapping Mashiba's story, and i'm not sure this Mashiba becoming world champion arc really adds anything other than maybe Mashiba accepting Ippo's relationship with Kumi, at least it should've been shorter. We got a Ippo x Mashiba spar that was fun, but that's it.
I'm not saying Woli's fight wasn't worse, but i've been following this manga for 15 years now and this is the first fight that i am struggling to care even a little bit about.