The do not call list seems to be a "Spam me, you brute" list.
In the beginning, they seemed to take their job seriously, but I doubt that has been the case for many years.
Right after SHAKEN/STIR was passed, I got zero spoofed calls. I did get a few robocalls, but they weren't spoofed.
For a month or so. So that shows the problem can be solved, legislatively.
Then, they started coming back, and now, almost every call I get, is spoofed. This includes some legit ones.
Also, legit callers should keep in mind that the autodialer companies they employ, might also moonlight as spammers, so they get blacklisted. I have had quite a number of legit calls get listed as spam.
Cynically, I feel as if politicians are unwilling to get tough on these, because they (or their proxies) use them. That seems to be both sides of the aisle.