Many in the crypto and privacy community mistakenly trust Telegram because it’s “end to end encrypted”, but there are huge issues including not hiding the metadata, censorship, centralization, and phone numbers.
Send this video to your friend that asks why you won’t join:
https://video.simplifiedprivacy.com/why-telegram-sucks/
I think it is quite well known that only Telegram Secret Chats are true E2EE. That said, Telegram is still not in the business of selling metadata actively like Whatsapp/Facebook/Meta are. As far as plain features go, Telegram is streets ahead of Whatsapp. But if I needed real “secret chat” I’d probably use Threema, SimpleX, Nostr, Jami, etc where I’m not tied to my mobile phone number or e-mail address.