have similar experience. struggled with Matrix/Element and with Signal too. the only app that works for non-techy audience in my experience is Telegram. i got several people to stick and continue using Telegram while i did not succeed with the other two. i guess better than Whatsapp in any case!
on the other hand, we use Matrix for all the communication in our little startup. we got some integration going on such as rss feed and notifications about new signups etc. works great as a Slack alternative.
Signal is one of the few good ones that show promise. They manage to deliver usable features. One fantastic thing is extremely picky userbase that's nagging about small details in the community forum.
The developers seem to really get average users, and the commitment to privacy over feature adoption schedule means every feature is as polished as the latest cryptographic design allows it to be. This means every feature is an actual feature that gives more power to the users.
Sure, there's stuff that indeed needs improvement, like usernames and registration without phone numbers, but once those come, it's likely to be polished enough not to require sudden knee-jerk patches like adding Google Captchas because a billion cryptocurrency scambots suddenly started spamming everyone, and there was no private Captcha alternative available.
I love that Signal doesn't consider privacy an individual feature (like Telegram Secret Chats) or Matrix opt-in E2EE (something that was the case at least in the past). Everything is E2EE, it's an integral property of every feature, there's no risk of downgrade attacks because the codebase never contained a non-E2EE implementation of some feature in the first place.
When working with TFC, I wanted the same with advanced properties like Onion Service based anonymity for everything, as well as endpoint security against key exfiltration, which I knew meant almost non-existent userbase due to the architectural design that requires custom HW data diode etc. I consider myself in a privileged position, I didn't have to consider every average user and that was almost exclusively due to the fact there was already a usable solution for networked TCBs, i.e. Signal, and a usable anonymity solution for networked TCBs (Ricochet and later Briar and soon cwtch.im). So I'm glad I didn't have to reinvent the wheel. Signal, Briar and Cwtch are _the_ interesting platforms. Signal is slowly taking over Telegram in terms of usability, while Briar is experimenting with an incredibly fascinating stuff like blogs and forums hosted on your personal devices' Onion Service. You could theoretically run a clone of any social media platform page for yourself from your phone, once average phones are fast enough and use fast enough Internet (5G/Wifi6 etc) to make Tor snappy (enough). Who knows, perhaps by then Signal will also run over Tor.
Signal still has usability annoyances, like this one where they decided to remove the UI for creating and leaving group chats from the desktop version in an impulse half a decade ago, and have refused to add it back again since.
on the other hand, we use Matrix for all the communication in our little startup. we got some integration going on such as rss feed and notifications about new signups etc. works great as a Slack alternative.