I think you're bringing a different but real issue into play here: Are 80 year olds more susceptible to scammers in general? You can assume future scam callers

I think you're bringing a different but real issue into play here: Are 80 year olds more susceptible to scammers in general? You can assume future scam callers will pass the carrier block because it'll be ubiquitous if free as Pajit proposes so the carrier-based block will lose its value to the frail elderly. More directly responsive perhaps: An add-on device resembling a stand alone caller ID display that can terminate forged calls or pass them through while inducing a warning message on the late 2000 telset display, your choice. My fear is as with the anti-robo call laws, carrier-level blocking will arrive with exemptions for political and charity solicitations and the like that some non-negligible number of end users would prefer to avoid.