In the US, the FCC has mandated[0] implementation of STIR/SHAKEN[1] by all the major telecoms by 30 June 2021.
That should take care of most spam/scam calls, as it requires the telecoms to verify that the callerID data matches the source of the call.
This won't eliminate such calls, but it will make it much harder for spammers/scammers to run their robocalling projects effectively.
One of the issues we have in the US is that telecoms charge the recipient for these calls, not the originator. In some (many? most?) other countries that's reversed and such activities are much less prevalent.
I imagine that once STIR/SHAKEN is fully implemented, a variety of actors will step in to capitalize on the opportunity to provide blocking/tagging spam/scam calls as well.
As with most things, there isn't a simple, singular solution.
[0] https://www.fcc.gov/call-authentication
[1] https://en.wikipedia.org/wiki/STIR/SHAKEN