That's true, but if you have unusual requirements that make GitHub impractical, there are other options. Devs can update their origin to point at a shared SSH server and coordinate merges through email or Signal or anything else. I think that's a lot more practical than hoping GitHub adds something like end-to-end encryption, or worrying that they might train their LLMs against private code.
There is a reason why people use hosted Git services it's not practical for everyone to "self host".
We can run a self hosted Signal app for privacy. But it's neither convenient nor practical for everyone.