If this is the issue, one of those forks will become the new mainline repo everyone contributes to. Expecting a maintainer to behave the way the community wants is unreasonable. Maintainers are not public servants.

I mean, anyone can fork it and become a maintainer, and create new guidelines and inclusive rules that ensure the project is steered in the "right" direction. Isn't it the case?

I understand the "we just want a better actix-web", but there are two conflicting concepts, "better", and "actix-web". The way I see it, "better" is whatever the maintainers think it is, and "actix-web" is a project belonging to its maintainers. No community should ever be entitled to try to steal that. They are welcome to build upon it and fork it. This doesn't mean they have to separate ways forever: some forks live happy parallel lives, as so many Linux patchsets have demonstrated over the years. Projects are free to be born, forked, cross-pollinated, merged together, even die, all at the will of their maintainers.