Anycast routing is not a DDoS mitigation method. It’s a system mainly used for load balancers and DNS servers where you want to be able to deploy servers in multiple locations across the world and people to be routed to the closest server. Applications using anycast are a little bit more resistant to DDoS attacks, because DDoS traffic can bring down only one POP but not others, but it’s not exactly DDoS protection.
And anycast doesn’t really work for web hosting, because most sites have a single, central database which requires them to be hosted from a single location.
And “AI filtering” doesn’t really make sense to me. AI inference is incredibly computationally expensive, and running it on attack traffic is orders of magnitude more costly than just getting enough capacity to handle the DDoS traffic.
Cloudflare and Akamai can handle DDoS attack by just being very big companies with a huge amount of network capacity, as well as not doing a lot other than handling a lot of traffic, so they are really good at doing it efficiently. CDN companies don’t really have any special tricks to block attacks.