Read the article - "Whether this is a good thing for the world is another question, one muddied by how poorly understood Telegram is, especially in the US. The vast majority of journalists still refer to it as an “encrypted messaging app.” This description unnerves many security experts, who warn that, unlike Signal or WhatsApp, Telegram is not end-to-end encrypted by default; that users must go out of their way to turn on the app's “secret chats” function (which few people actually do); and that only individual conversations, not those among groups, can be end-to-end encrypted. For the millions of people who use Telegram under repressive regimes, experts say, that confusion could be costly."

Even if you make the argument that telegram CAN be encrypted (only in 1-1 chats) what ultimately matters is how people actually use it, and that is probably in an unencrypted manner.