These is another reason Ractor is not used: it's an experimental feature that logs a warning the first time it's called. If core developers desire gems to start adopting it, then they have to at least advertise it as stable enough and remove warnings.
I've tried to implement some functionality around it and reported issues. In my care it's just the lack of time that keeps me from completing the work.
Yes, this was the main reason I did not use Ractors fully. Because of the warning about it being an experimental feature!