I always see Signal as being "really good" crypto. Bulletproof? No, surely not. That doesn't exist. If I were a dissident or something I would be using gpg religiously and all that jazz.
But is signal significantly better than basically every mainstream sms-like thing? Absolutely! imessage, sms, mms, whatapp, facebook messenger, whatever google's current chat app is, etc. All of them don't even try to be a secure/privacy-respecting chat tool and reall y make no secret that they're usually totally the opposite (facebook messenger....).
So when it comes to getting my parents onto something that sends videos of the kids real good and also will make dragnet state surveillance efforts a bit harder, I pick Signal.
Agree on the second part, but two messaging solutions can and should be compared. 1-to-1 (text/voice/video) messaging is entirely possible with both Signal and Matrix, and evaluating that narrow use case is a reasonable way to compare the two.
Matrix doesn't use phone numbers, and is federated (that's what makes Matrix interesting), so it's naturally the "antidote" suggestion on threads when people bring up these aspects of Signal.
The fact is that they're not really comparable projects; they have different audiences and different goals. People have an innate narrative bias that constant hunts for horse races to spectate, and so you'll see a lot of "Signal vs. Matrix" arguments, but it's an artifact, not anything substantive.