There is a degree of rational fear, rational expectation of being tracked. Your degree of fear though is irrational unless you are, in fact, a journalist in an authoritarian state.
You are saying that you are so paranoid, you don't trust iMessage to be End-to-End Encrypted because it has zero-click exploits developed as part of a cyberweapon that is explicitly targeted against high-profile journalists. You then think using Signal or something is more secure, even though if this was pulled off in iMessage (more sandboxed than any other messenger security-wise), your other messengers probably are also flawed and you shouldn't use any of them.
In fact, you shouldn't use a mobile device. And maybe for your situation, that is right and rational. But for most people, it's not.
