Honestly I think each of them should've had their own film first. So you have a point here. Obvi that would make the story completely different but yeah.
If they was the case it could've been a movie like you're saying that is the aftermath of her perspective changing. Now she knows she's powerful, and now she knows that she needs to use her powers with wisdom. But how do you gain that wisdom? You make mistakes.
In the first film people complained that she was overpowered and pretty much a dick to everyone that came in her path. (Motorcycle guy amirite) so maybe she deals with the aftermath of nearly genociding a planet and realizes that where in the first film she was being limited by outside pursuasions, now she must limit herself and determine the level of force necessary for each job. Maybe she learns that she needs to stop and strategies rather than fly in punching.
And that leaves me thinking a part of why the marvels feels so messy might be that it was separately 3 films and that they smacked em together because the ideas they had were to small for each one? Because after reasoning this out, I really feel like the part of the movie that worked and almost made sense to me was kamala's bit.
If it has been her movie and she was swapping with the bad guy because the bracelet, that endangers her parents. She learns of Darben and the fact she absolutely hates Captain marvel (gets transported to get room. See all the posters and fan fiction. Terrorizes the house and her family meanwhile ms marvel is on the spaceship like wtf? Then they switch back and get home is destroyed and her family hurt and S.A.B.E.R. is showing up because of satellite surveillance and yadda yadda) she would have seen another side of captain marvel and would try to defend her only to little by little have all her thoughts challenged in the film. She becomes more herself and distracted herself from loving Captain marvel so much, until she herself has to make a hard decision too and boom. Now she understands that some people are just going to see you as the bar guy. You can't save everyone. You need help sometimes. Teamwork. Young avengers can still happen and she regains her original respect for Captain marvel.
Then I dunno what to do with Monica for her own movie. But with this logic I think that leaves all the space stuff that was in this film too supposed to bring her movie? Jump points and science and alternate dimensions.