Re: Signal vs. Others
You might be getting confused with Telegram, which does have its own home-baked, and apparently somewhat half-baked, crypto system?
Crypto is indeed hard to get right, and we are all better off using systems which have been peer-reviewed by experts in the field and proven(?) to be robust.
Signal's Moxie Marlinspike is reputedly well respected for his cryptography and security knowledge, but, given the subject and what is potentially at stake, there's always that small nagging doubt that potentially a double-bluff is being played, and that that's what They want you to think...?