End-to-end encryption on Telegram is only available as a ‘secret chat’. These are only between two devices and are not synced.
The thing is that iPhones are used in all kinds of situations, including by professionals. It is absolutely fine if I want that kind of interaction in Facebook Messenger, but Messages is also the only SMS/MMS client that we have on iOS. I want it to have a more sober tone and don’t want to see fireworks, stickers or huge emojis. I do know people that like to use these things and I know that it is going to annoy me.
Look at WhatsApp, their offer is bare-bones and yet they have by far the most popular client. WhatsApp’s capabilities have always been subpar to the competition in almost every way and yet their growth has even accelerated, especially after Facebook took them over. Apple does not compete with WhatsApp, they compete with the relatively smaller clients, notably Snapchat and Facebook Messenger. I think that this is not worth it. Apple doesn’t need to compete with every popular app, they should offer a strong foundation for developers and good basic apps. IMO, they shouldn’t try to do the work that developers are already doing.