For PvP; The targeting system is broken. Combat is simplistic and reliant upon numbers. Ram is a faggot. The world is so big I can never find anyone.
I'm not sure I agree with most of these things yet but I don't think I'm qualified to make much of a statement just yet, I'm only repeating the opinions of others. I do however enjoy the idea of having a siege tower which I've seen mentioned here
The river system is worse than that of legacy, traveling is a pain in the ass right now and the map is bigger than the sun. Stitching the top and bottom and the sides together to make a spherical map would reduce the effective size of the world somewhat but I just like that idea because it sounds cool.
I don't think those are the main reasons anyone has stopped playing though. I think the real reason is that at some point the game becomes nothing more than logging in to grind purity. There are no fun little random events which can pop up. You aren't going to open your chicken coop to discover a three headed chick has hatched, although one time in a billion you might find a golden egg.
Fate has destroyed foraging altogether and there is now much less reason to venture outside for those few who ever did.
I think the games primary playerbase consists of frightened carebears who get bored with a lack of content and spice to their purity grind, and then there are the PvPers who are struggling to get enjoyment from a system where all manner of PvP lacks variety and the same element of spice or randomness. I don't know how to fix PvP but I know that fleshing the fate system out by either increasing the chances of fate events occurring or increasing the number of potential fate events would go a long way to alleviate the boredom of the end game purity grind.
I also think it's garbage that an entire town can be levelled during a PvP event. There are things I've mentioned in the past which would make it much worthwhile to actually take and hold a town you capture or to rebuild it after a raid. Giving us a way to improve the output of our wells and such would go a long way towards this.