We each have our own levels of acceptable privacy posture. Signal make it easier for the masses to get off, say, Whatsapp and feel little to no real hurdles. I agree with you, though, that the phone number and physical phone requirements are a hard sell for people with a more strict posture requirement, which was the reason it took me long to get on it. But, alas, I had to settle, because SimpleX wasn't available on iOS at the time (my family and friends are on iphones) and it is much more private that Hangouts or Whatsapp (which I still can't believe we were on). We did try Matrix for a time, but it wasn't "production ready" then, which was a deterrent to them as well. Signal being centralized wouldn't be a huge deterrent for me, if it wasn't for their continuous push to keep it that way and them actively preventing decentralization, both of which have been scratching me the wrong way for a while. I had a conversation with my groups to switch to something else, but they're not all on board. Signal, they say, is "as easy as Whatsapp and more private". I mean... they're right, but we could have better.