The CDN part is kind of pointless because they can't really have nodes in large parts of the western world since.. it's a warez site. The CDN providers will get takedowns, requests to reveal the backing origin, etc. You can't use a commodity CDN provider for this.

In their case (manga), seems like the vast majority of the content is cacheable.

Latency makes a bigger impact on UX than throughput for general browsing. A TLS handshake can be multiple roundtrips that greatly benefit from lower latency, especially mobile devices.

Modern CDNs also provide lots of functionality from security (firewall, DDOS) to application delivery (image optimization, partial requests).