I chatted with them for 3 hours. The agents didn't understand the issue. It was really clear they don't actually know how crypto or even Coinbase works.

This is not a case where the money is lost. They actually have the money, and are refusing to return it, while saying "transactions are irreversible." Yes, so create a NEW transaction to return the money. I told them this and they refused.

If you mail cash or other valuables to the wrong address by mistake, there's actually legal precedent that the receiver has to return it. So I think it would be possible to sue Coinbase and win. It's basically theft.