The continuing defeat of Shadaloo is a separate issue from whether or not Rashid should be part of the story.
If you plan to keep introducing new characters to a series, then at least some of those new characters should play a direct role in the new stories. Your argument would also say that Alex should not have played a part in SF3’s story, Juri shouldn’t have been involved in SF4’s story, and F.A.N.G shouldn’t have been in SF5’s story. We should just keep seeing Ryu, Chun-Li, and Guile dealing with everything, with Akuma lurking in the shadows?
Though perhaps Akuma never should have been added into the mythos; Ryu had already been defeating M.Bison for four games before Akuma was created to jump in and beat Bison instead.
Guile matters? Yes, he has a connection to Bison, but when is the last time he really mattered? SF2? The Jean-Claude Van Damme film? He initially wanted revenge, but presumably learned to deal with it, and has since just filled a generic military presence role that could be equally filled by any faceless figure.
Chun-Li is in a somewhat similar situation to Guile, except she doesn’t even get to move on. Capcom can’t afford to let her move on; she’s too popular of a character and will keep being brought back.
When you get down to it, if you want the story of Bison, of Shadaloo, of Street Fighter as a whole, the only character that is absolutely necessary to the story is Ryu. Every other character is interchangable and disposable. SF story revolves around Ryu even when Ryu himself is barely part of the story.
You can slot any of the multiple existing “revenge against Bison” characters into a “revenge against Bison” roll. You can slot any of the multiple existing government/military figures into a government/military role, or shift another existing character into that role, or just create a new one. There are multiple Psycho Power related characters and/or potential Bison hosts for any story you wanted to do there. You could swap out any of Bison’s underlings.
You don’t even need Cammy to do a Doll-related storyline at this point, as you have (doll) Juri, Juni, Decapre, and even slightly related characters like Han Juri to handle such a storyline. You could even fold that into an objective of Neo Shadaloo, which is on its own push to rescue the victims of Bison.