Why does it "really hurt" Signal that are sub-group of the population is ignorant of its features? I doubt that's going to stop people from downloading a privacy app, most people don't care about privacy anyway, and if they do, they will DL signal.
Having a slightly worse UX because that's just security considerations is one thing.
Having a slightly worse UX because reason that isn't related to security is another.
I've tried getting my wife onto signal, and while she's happy to try it out because I ask her to, she struggles to stay on it due to by day to day UX. I'm happy to deal with the issues, the general is not. And because they're not, I'm stuck with WhatsApp too.
If signal wants to have a shot at taking over WhatsApp and help with addressing the core issue at hand, specifically encryption between users, they need to address the UX. Sure if you can't address certain things because it weakens security fine, but if you're not addressing them because they think users won't mind because they're here for something else (i.e. security), it's gonna be a much harder sell, and it'll just stay a niche market.