Your group chats go into a black box unencrypted. You don't know what happens to it because it's not E2E. You also gave your phone number to this shady company who runs those servers which keep everything you wrote.
Even Whatsapp is better than this.
And what is that phone number fetish? It's not like it is some magic identifier. There are bots out there testing every number out there and sending you SNS spam. Your phone number is worthless.
As far as I remember, you can still find people on Telegram by searching for phone numbers. Isn't there even an automatic discovery feature?
The Telegram salt around those announcements seems like the final cry of Telegram fans to me because after that, there is absolutely nothing which would even remotely paint Telegram as a safe or secure messenger. Especially because everybody know why you are on Telegram. It's a different use case. I talk on Signal to people I know personally. They already have my number. People I know go on Telegram for porn and piracy over here. They still have Whatsapp or Signal to talk to their friends and family. They actually are ashamed that they have Telegram because everybody here know why they have it ;)