The 'Ask Reason for Calling' iPhone feature has completely eliminated scam calls for me. Real callers not in contacts leave a short message and I pick it up. Best iOS feature from the last few years IMO.

Have you added yourself to the Do Not Call register?

https://www.donotcall.gov.au

I don’t think this will cut down on spam so much as fraud. All spam calls I get don’t have registered IDs