Don't let perfection be the enemy of good. All my friends and family use Signal, it was a multi-year effort to pull that off. Signal will roll out usernames faster than the tide will turn, so let's take our wins and learn to be better.
I can't fathom why they insist on sticking with this. It's so obviously a de-anonymization technique, which is completely at odds with the rest of their stated goals. I haven't made a Signal account for exactly this reason.