None of this replaces email.
A big one is I am not sure I will have every Telegram chat I received a decade or two from now, and I will have all my email.
Another is everyone uses email. Not everyone uses other apps. So far Telegram is entertainment only. That is fine.
Email can act like chat, chat is not email.
I very strongly disagree with better. Different? Yup. More experiences possible? Yup.
But not better. Email is killer. And it is not hard, is time tested, production proven, near ubiquitous.
UX is bang on simple, and I hardly ever think about it.
"Better" needs some reevaluation to be frank. I see a general failure to understand why email is great. That means a claim of better UX may make very little sense.