They don't have to block anything. Just make sure that any caller id number is validated and registered to the company making calls. I shouldn't be receiving calls from local numbers that are actually Indian call centers threatening that the police are on their way unless I pay my IRS bill with iTunes gift cards.

Services like twilio avoid this easily by simply requiring me to purchase the callback number or at least validate that I have control of the callback number I want to use.

As I understand it, there is no way to validate caller ID when it comes from another carrier. They're testing STIR/SHAKEN which supposedly fixed this, although I'm unclear on how long that will really take to roll out and actually be turned. I'm also unsure how well it will actually work, I haven't looked at how it will be implemented.

While robocalling should be blocked, they need to give consumers power to block their own calls by forwarding the originator information. The CallerID simply allows for deception, but if you provide the originator information and I know the call is coming from a country where I don't know anyone (whether it be the number, a voip address, or a shady phone company) I can preemptively block them adblock/ubo style and share that list collectively with my friends and the internet. Anything short is only going to delay the death of the relevancy of the phone number.