On: FCC will require phone carriers to authenticate calls by June 2021 [pdf]

[user5994461]

and indeed gmail has fixed email spam for almost 20 years.

[unishark → user5994461]

Spam filtering is based on the content of email. To translate this (partial) success to phones, we'd have to let a private 3rd party monitor phone conversations, record them on its server indefinitely for training their AI, and screen them for us based on what the caller is actually saying to us.