Yeah, they use a completely different (way newer) server and client. It's probably the newer client that makes most of the difference here, not the newer server.
Deep Island uses a client that was only ever intended to work offline, but had a lot of online stuff still left inside of it due to even earlier days. It is a miracle that it works online at all.
![Wink ;)](./images/smilies/icon_e_wink.gif)