It is true that Shizuma and his group have been defeated, but it takes time and some battles first before Boruto and others win, even with the help of Chojuro the Mizukage. Why take a long time against Shizuma and the others despite Mizukage already there?
It happened because as a Mizukage, Chojuro certainly restrained himself from exaggeration. If he wants, then he can easily defeat Shizuma and others. However, what if we change, not Chojuro who helped Boruto, but Suigetsu?
Of course the story will be different. Unlike Chojuro, Suigetsu is a reliable killer and certainly has no compassion. Even Kisame Hoshigaki alone acknowledged that Suigetsu was the master of murder. He will not hesitate to torture and mutilate his enemy first before killing him.
The first goal will not be realized if the second goal is not met. Against Kisame may be difficult, but what about Shizuma? Surely Shizuma will be an easy opponent for Suigetsu, even Boruto who is still in the Academy can defeat him.
Further, perhaps Suigetsu will also fight Kagura for Hiramekarei's sake. If this point occurs, then Boruto will not remain silent, and ultimately help Kagura to defeat Suigetsu. Directly, Suigetsu also violated Orochimaru's order not to make physical contact with Shizuma's coup attempt, and indirectly opposed the peace agreement of the five villages, the problem became more complicated.
Since it will be complicated, Suigetsu does not act, though Suigetsu, the writer himself, and maybe some of you want to see Shizuma beaten up by the young man who can search for this, and do you also include? If so, write your opinion in the comment field yes.