I built a community that aims to keep FOSS projects alive. It's meant to solve the kitchen and egg problem by having as many people and projects sign up, and then any developer who was interested could just automatically get commit permissions to any project. It's called Code Shelter: https://www.codeshelter.co/ It's stalled for a while, so I don't know how viable it is, but I'd appreciate any help.
For example, I use a javascript library that's best in class for what it does, and yet hasn't had any real commits from its maintainer since 2016. There are 50 pull requests open, some of which fix significant bugs, or add good new features. There are literally 2000 forks of the library, some of which are published on npm but are themselves unmaintained, and almost none of which link back to the actual fork's code from npm. It's a mess, and I bet it's a situation repeated hundreds of times over.
If you were to figure out a workflow by which a maintenance team could form on your platform, and then a) the existing maintainer is pinged to request that they add the team, falling back to b) making it easy for the new team to fork and adopt existing pull requests while supporting them through initial team-forming by laying out a workflow for assigning needed-roles, then I think you'd have a valuable platform.
The key thing is ensuring there's a large enough team to start, so that yet another fork doesn't die on the vine, so maybe think about a(n old) reddit link type interface where people can link to, vote on, and volunteer for projects, with no work needed until there's critical mass and the platform moves the project forward.