There is no point in end to end encryption in public channels, so this specific criticism is not valid.

> I don’t quite understand what the point of telegram is then?

It's UX is far superior to any cross-platform competitor. On top of that, its client is open source and the servers have easy and free bot APIs. It also has channels, which broadcast your messages to followers and many secure competitors don't have such functionality.

It's not encrypted, but as it turns out most people don't really care about that in practice. If they would, texting wouldn't be popular in places like the USA. That's probably why people go to Telegram instead of Signal, ease of use is more important than privacy for most, especially in group chats that are generally about what's for dinner.

Having E2EE in a large Telegram channel would be like having an E2EE Facebook group, subreddit or even a web forum.

If something leaks, it's through users, not through someone listening in or MITMing the communication.