Funny, the same telecoms that whine about how hard this traffic is to stop... are also selling a "premium" service to customers- who then manually tag unwanted calls so that the telecom can sell that data back to other customers...
For spam mitigations to work, the cost of selling that business must exceed its revenue.
Some, and I won't mention AT&T by name, are very curiously opposed to any regulations touching this.
<https://www.t-mobile.com/benefits/scam-shield>
The free tier seems to identify but not block likely scam calls. T-Mobile's website skews sales-heavy, and doesn't feature much technical information.
The premium features appear to be app-dependent, and may not work on feature phones.