Arguments why Telegram is not a good idea for anyone

Hi :) I know that Telegram is not save and not a good messenger if you are a privacy-geek. Sadly some parts of my family still think so. I brougth up the arguments, that they are cooperating with Russia, that they or closed-source on the server-side and that e2ee is not on by default and only available for 1-on-1 chats.

My question now is, if you gals and guys might have some other arguments or sources I could use.

I don't want to convince anyone to switch away from Telegram (because I am no missionary :D) I just want people to understand the risks of using Telegram.