Do you really think that criminals pay attention to the Do Not Call list? Only legitimate business pay attention. The DNC does work for legitimate business. I understand your frustration but how naive to believe any scammer will heed governmental warnings. Most are off-shore anyway so nothing can be done legally to stop them. Blocking is the only answer.
Get a Call Blocker V5000 on Amazon! That's 5000 slots for blocked numbers and it blocks whole area codes if you want and automatically blocks 'Unidintified' numbers and weird numbers like 000-000-0000. I have the older one which blocks 1200 numbers. I'm only at around 300 blocked now but if I ever need more I won't hesitate to buy the 5000. They have great customer service. Amazon still has the slightly cheaper 1200. The company is in England and no I don't work for them. I just love the quiet I have in my house now!!!