I'm not sure if "OpenCASCADE is just not a good enough" in the architectural sense or if they just don't have the manpower. When I looked into some bugs a while ago it sounded like "yeah, we've know this bug for years, we would like to work on it but don't have the manpower right now". Just adding outside contributions to such a project is probably also not possible because the components interact in many ways and you have great potential to introduce a lot of subtle bugs.