The remaining criticism now is that the default for one-on-one chats is still the more convenient normal point-to-point-encrypted chat type instead of E2E-encrypted (which, in Telegrams implementation is less convenient since it doesn't sync between clients, which again is reasonably for those messages where one really cares about secrecy in the context of day-to-day messaging apps).
As usual: I only observe this from the outside. For what I know maybe Putin reads my messages before he goes to bed every night to fall asleep because I mostly use ordinary point-to-point encrypted messages which can be intercepted if Telegram is a secret FSB front or if Telegram isn't careful. Note however that for all we know maybe Biden reads my mail too to fall asleep since that too isn't end-to-end encrypted.
I only comment on observable facts or statements that haven't been debunked. The last means I haven't verified the crypto of any app, I take it for granted that if it is broken someone will figure out just like when WhatsApp sent plaintext messages over port 443, and even faster with Telegram since there are so many who wants to find flaws in it.
If you have and you have real proofs, bring them and I'll probably repent.
In light of that hypothetical but far-fetched pathway, there is probably no need for you to repent there.
With WhatsApp the claim was that if someone snuck a backdoor into it there are enough people watching it to make sure that it would be found out soon.
My point is that even more people are sceptical to Telegram and even dislike it strongly so there should be even better chances of someone discovering if something was broken.
I'm honestly interested.
I only intend to defend Telegram against lies (most of the time the claim that "it is not encrypted"), not to cover up any actual problems so if you comment on it or write a post about it I will read it and probably will upvote it.
And Telegram most certainly cannot encrypt group chat.