d9780 SMS is considered a legacy communication standard, due to how carriers implement it, any 'anonymisation' or 'encryption' on a device level will never compensate for how the standard works and the transmission of data in plain text across the carrier network, always being susceptible to MITM.
While I disagree with Signals decision to remove SMS integration, one of the reasons being how TOTP SMS will no longer be secured inside Signal, this was always a local concern and not a network one. It would be ideal for all OTP to be done via services such as Aegis, Microsoft/Google Authenticator etc at the very least or by using U2F at best, most services refuse to as SMS OTP reduces the cost burden both financially and user education in implementing such practices.