Game is from 2010, visually updating a hugely popular MMO that's this old can take a long ass time, especially when your walking the fine line between adding modern visual techniques and still having the game be able to run on the majority of the millions of pc's currently running it. Also the game still has to run on the og PS4, which is getting some visual improvements itself.
Could be worst, at least they stopped supporting PS3, if that version was still running we'd probably get none of this.
I imagine the game will still have some kind of potato settings. when you have like 30 million monthly players you gotta have some support for the weaker hardware too.