Any list that has enough accuracy to be useful is valuable, and isn't going to be available for free.
Perhaps you've heard of https://www.nomorobo.com/ ?
Perhaps you've heard of https://www.nomorobo.com/ ?
What about the URL blocklists all available for free then? The are indeed very valuable aren't they? Why in your opinion aren't they available behind a paywall?
All of the ones that are of sufficiently high quality that they're worth using (new URLs reported quickly enough to block active senders in progress, not filled with false positives, etc.) are all paid subscription services.