Telegram is not a private messenger. It's a handy service that allows groups of people to organise publicly. It's quite censorship resistant in its geoarbitrage. It has functions that no other public messenger has that make group discussions easy.

No one is claiming Telegram is private. It's not. It's as public as Internet forums or Twitter. Only, Telegram is much more handy than these.

Telegram is where in many cases the real discussions happen about topics like private bitcoin. In other words, you're not going to find most of the NGU or Lightning peddlers on there.

I'm not even sure if a private messenger could replicate the functionality of Telegram. And that's fine. For public discussions: Telegram. For private discussions: your preferred private messenger.