This is wrong. The ClientHello message is not encrypted in TLS 1.3, so, the client has to announce any extensions in plaintext. Thus the Great Firewall blocks connections which say they want to do encrypted SNI.

TLS 1.3 works fine in China, but if you use TLS 1.3 with the earlier proposed encrypted SNI draft it is blocked. The Great Firewall can't tell which name you actually wanted, but it can tell you're encrypting the SNI and block that.

With the currently proposed Encrypted Client Hello with a GREASE-style dummy ECH on all connections (so the "real" Hello is sometimes in an encrypted block and sometimes that encrypted block was just noise), China would still be able to choose to block all ECH-enabled connections since their presence is detectable. This would break everything, but China can choose to do that. What happens next is a policy question.

If you want to sneak past nation state snooping you need something else, that's not what TLS is for. The TOR project does not directly offer this either, but they can help you find out how to connect to TOR in a sneaky way if that's necessary for you.