There are many Telegram users who think they are communicating in an [end-to-end] encrypted way, when they’re not because they don’t realize that they have to turn on an additional setting.
There’s no reason not to use end-to-end encryption for your messages by default, especially as an application that brands itself one that makes security a high priority.
Clearly, Telegram’s security isn’t nearly as robust as WhatsApp’s or Signal Messenger’s.
So the point is, if you’re looking to communicate securely, just use Signal, iMessage, or WhatsApp. Telegram has too many potential flaws and hiccups that may compromise its integrity as a secure messaging application.
Here's a chart which can help you decide what messaging app to use.
See you on Signal!