The Do Not Call database in the US has never been effective because the type of company making these spammy calls doesn't care if they are breaking the law. There is no enforcement effort to track them down.
Do you remember what things were like before the Do Not Call database? We would get one or more marketing calls a day on our home phone (landline). These days, maybe once a month.
I've been on it for years as well as the DNC database for caregivers of elderly patients with diminished capacity and I receive more than 5 calls per day.
It's exactly the same situation with the Telephone Preference Service in the UK in my experience. The only way I've managed to get these calls to stop is to get withheld numbers (ie callers with no or blocked Call ID) blocked at the phone company level - which usually incurs a monthly fee, of course...