There are already at least two geometry kernels being written in scratch in Rust (see fornjot.app for one) --- the problem is the first parts are obvious/easy, so initial progress is rapid, then one hits the difficult/intractable parts and progress stalls, usually to be abandoned.

There are a couple of doctorates available for folks who are willing to research and publish in this space --- the commercial products are all holding their solutions as trade secrets in their code --- even then though, the edge cases are increasingly difficulty to solve in such a way as to not break what is already working, hence the commercial kernels having _very_ large teams working on them, or at least that is my understanding from what Michael Gibson (former lead developer of Rhino 3D, current developer of Moment of Inspiration 3D) has written on the topic.