Protip: security is not black and white
The word "secure" is not binary.
sms as a 2fa is secure.
Just not as secure as a authy totp account
...which is not as secure as a unclonable totp system
...which is not as secure as a hardware token based otp system
...which is not as secure as a hardware token that also requires you enter a pin and a fingerprint to activate it and only communicates using hard coded encrypted messages with the legit service that issued it.