I understand, that mobile phone verification is probably the most convenient way to validate real users and avoid spam, but those "secure/private" messengers are afterward still bound to phone numbers, and this has inherent vulnerabilities with regard to security - your whole account depends on SMS codes (and as discussed many times GSM (sms) technology is purely vulnerable).
The solution could be if the user could set up a username & password (or 2FA TOTP code), thus the phone number could be stripped from the account. However, I was unable to do that with the top 3 "secure" messengers (ironically, Facebook/Google has that feature, after setting up 2FA, you can de-associate phone number from the account). Any way to achieve that with Telegram/Signal/WhatsApp? Otherwise, I don't consider these messengers as secure as I think of security.