Looking at Riri Williams, it’s weird, you could probably cut her from the film and not a lot would change.

You’d need to find a different reason to introduce Namor, but after that Riri just kinda hangs out.

She goes with Shuri to Talokan, but she’s unconscious when she is taken there and just sits around until they leave.

She makes a cool suit for herself. She might have helped with the Midnight Angel armor, but it’s clear Shuri did the bulk of the design. In either case, while cool, none of the armor created is key to the end battle.

Obviously Shuri is smart, so having her struggle and then Riri just show up and solve things would be cheap. Maybe they could have leaned more into Shuri being angry and that causing her to mess up or be less receptive to feedback.

Riri was also the only one able to build a vibranium detector. Maybe find a reason for her to swear she’ll never build one again, stay behind but still have Shuri taken to Talokan, and then Riri builds another one. That both justifies Namor’s distrust and Riri’s importance.