Are you looking for arguments against Signal?
I think the biggest one everyone will find and is very difficult to overcome is “My friends aren’t there”.
Other arguments like “it’s centralized”, “It’s in the US”, “It doesn’t have feature X”, “The client app doesn’t have fancy stickers” are workable, have explanations or are a matter of time.
Thos saying “It needs to support SMS”, are americans that weren’t really using signal, but a glorified text app.
Signal and whatsapp (due necessity) for daily life. Slack and email for work stuff. Rarely send personal emails anymore.
I Spanish, the Real academia de la lengua is often used incorrectly by people as a prescriptive reference but what they really do is gather the common usages and incorporate them into the language. It’s like a descriptive record of language.
I’m surprised at Telegram, I expected more information to be available, since it’s a central database with all conversations. But I can see how they simply don’t collaborate and protect by obscurity making data unavailable.
I feel more the lack of my favorite communities that haven’t made the jump. Some alternative attempts exist here but are dead. I miss the variety of topics and random discovery as well.
They aren’t E2EE so all messages and activity are recorded. They are subject to to very different rules than regular chats or groups.