Technically no one is stopping hearing people from learning sign language. There’s always exceptions, but majority of hearing people do not know sign language, or if they do they aren’t as fluent as deaf people. Of course there are people who have chosen to learn sign, I have a friend who just decided to study ASL in college and works as a translator. And there are hearing CODAs.
However, the vast majority of us hearing people never learned to sign and are impaired, the same way someone who never learned to read is impaired.

I think my comment was to flip the narrative, but also trying to acknowledge the rich culture of deaf people that comes with their sophisticated language. There’s a whole world of culture and language most hearing people don’t experience, or may not even know about, and in its own way the hearing are impaired then because they lack the skills to participate.

But technically, hearing people are capable of learning sign.