1. Having to share the phone number is the biggest issue for me. This shouldn't be the case in 2021. I can only use Signal with my close friends. OTOH, I can confidently share my Telegram handle with anyone I have known for a some months, even online (not in anonymus forums, of course).
2. Notifications in one platform is weird for me.
3. Video quality is extremely bad to the extent of unusable.
4. Completely agree with the lack of settings whether other users with my number can text/call me on Signal.