The telcos might be a common carrier, but as the end user I sure as shit should be able to block calls originating from providers I see abuse from constantly. I'm looking RIGHT AT YOU, TxtNow.
Cell phones surface the SHAKEN/STIR attestation status to the user via a checkmark in the telephone UI.
If you want to programmatically act on that data to filter calls... Android provides access to the attestation level via the android.telecom.CallScreeningService API. (I can't speak to what iOS provides.) For VoIP, many providers will also either pass along the attestation level in the SIP headers or by appending some text to the Caller ID string.
If end users could directly and simply block carriers that waste their time by delivering shit calls, this entire issue would have worked itself out years ago. I just don't think that the current strategy of having the FCC yell big numbers at foreigners is really doing all that much...