Signal is not good for normies: compare sending a message with Signal to WhatsApp. Didn’t go through? WhatsApp will try try try to resend. Signal tries far less then shows the dreaded red exclamation point. Not great while travelling or with poor reception.

I spend about half of every year traveling the mountains and deserts of the world, often ones with poor infrastructure. I use Signal more than any other messenger app, and I have never had the deliverability issues you complain about; messages do all get through eventually.