This was pretty common until (I think) late last year, but GP was writing in present tense. The Matrix team have been fixing the various bugs responsible. I haven't seen an "unable to decrypt" error recently.
I don't really use Whatsapp, or any IM client on my phone, but do have a few friends use Telegram so I'm using it on my computer. We're looking at alternatives. We tried out Signal, and that feels extremely basic and spartan, like old ICQ or AIM. We tried Matrix (with the Element client) and it feels much more featureful and modern. And the federated aspect feels much better than the centralized nature of Signal.
Can you explain a bit more about where you feel the complication comes from?
This group of friends are mostly not very technical. They were able to create an account on matrix.org perfectly fine. They felt a bit strange that they had to pick a username "like in the past" and not use their phone number. But at the same time they felt pretty nice not giving away their phone number to a foreign company/organization.
Matrix makes progress, see https://matrix.org/blog/2023/09/matrix-2-0/ and the UX has improved a lot since Element X (compared to previous Element), especially encryption settings have been simplified (a pain point I myself discovered when onboarding less experienced people)
After a decade of holding on with a small pool of friends with Matrix, we finallly gave up this month over notifications dropping It hurts because I agree in principle - I don't even fully understand why notifications even should need Play Services or whatever Apple does. But after enough missed occasions, we decided it wasn't worth it and reverted to a blend of SMS and Jabber, where the notifications consistently work (on apps that dont use the above). I don't think the Matrix team is taking this seriousy enough. If you miss out on moments over dropped notifications, you or one of your group will fall back to another method and soon enough so will the whole group.
speaking as project lead of Matrix: i’m not aware of a general problem affecting dropped notifs. mine are fine on matrix.org on element x ios for instance. are you using unifiedpush on android on a ntfy server which is rate limiting notifs or something?