I manually add to block list,, which I just looked,, it's a very long list.
Unless I'm mistaken, adding a number to your block list in an effort to combat spamming calls in particular is an exercise in futility.
Spammers/scammers these days use software to "spoof" phone numbers when they make calls, which means they can make one phone number -- theirs -- LOOK like a different phone number to your phone's caller ID each time they call, specifically because they know you'll just block one number after getting a spam call if you keep getting calls from that same number. This method effectively gives them an unlimited pool of numbers -- effectively EVERY phone number on Earth, including even your own (as has happened to me once) -- to use to spam you with, and practically no real defense against it other than simply not to answer.
More often than not, spammers -- which often times set up their operations out of the country and therefore US legal jurisdiction -- deliberately use phone numbers that are dead-ends, disconnected, or not in service so as to make it even harder to report them to the police. On the occasions where spammers DO spoof the working phone number of a legitimate person, that individual may not even realize someone was pretending to make calls from it.
It's gotten so bad that it's made the news MULTIPLE times within the last couple of weeks here in San Antonio. Somehow the scummy bastards have figured out how to spoof the number to City Public Services (the city electric company), and have been making spam calls to thousands of people in town. They even called me personally, disguising their number as the legitimate, working, publicly listed business phone number for CPS Energy: (210)353-2222. My phone even recognized it as being CPS because I have it saved to my contacts list. Though I knew better than to fall for the bull (they pretend your payments somehow haven't been getting processed correctly for the last couple of months, and that they're going to disconnect your services in 30 minutes if you don't pay up $___.__ immediately), they've apparently successfully defrauded other customers out of hundreds of thousands of dollars already.
Blocking numbers is really only useful these days for blocking people -- actual human people -- that are harassing you and don't have the technical know-how to disguise their caller ID info. Though normally Apple is anathema to Gilgondorin, they should at least still be commended for trying to do something about this annoying bulls*** because it's starting to get insanely out of hand. I'm up to usually a minimum of 3, and sometimes up to as many as 10 spam calls per day, which is really frustrating because -- like Shield45 -- I can't tell which calls to answer and which to ignore, because a lot of people often call me that aren't on my contacts list.