You might just as well say that E2EE messaging is impossible because you are sending a message "to" Signal, and they need to read it in order to act on it.
I'm telling the bank "I want you to give $5 of my money to Bob". I'm not asking them to pass a message to Bob. The entire message is the instructions for the bank to give the $5 to Bob. The bank MUST be able to read that message in order to follow the directions. There's nothing to "leave encrypted" to treat the bank as a non-end of the E2EE.
You could presumably hide who Bob is by making it some kind of anonymous account thing... but that _still_ wouldn't leave any message encrypted. Because all of the information needs to have been decrypted for the bank to act on it.
For the Signal analogy to apply, there would need to be some message going to Bob. And there isn't... other than "We're giving you this $5 for OP", all of which is information in the original message that the bank needs to act on it.
You might just as well say that E2EE messaging is impossible because you are sending a message "to" Signal, and they need to read it in order to act on it.