If they were leaking there would be prosecutors using the evidence in court, on the public record.

It doesn't matter what infrastructure that they use because the service provides end to end encryption. This remains secure even if a third party is able to record all of the traffic between the two devices.

Has there ever been a single instance where a Signal client had a RCE exploit? Of all of the software on your phone likely to be exploited, signal is low on the list (your browser is where they get you).

Enshittification is a reason to leave, speculation about maybe possible enshittification in the future is not.