Everyone is entitled to their opinions.
I just wonder why (and you definitely do not need to answer) people who hate a game or say they've stopped playing feel a need to come to the forums and try to convince those who like the game and still play that they need to hate/quit. I mean if you've moved on then...well...move one for crying out loud. Oh I guess that is it...you want to CRY OUT LOUD.
There are a lot of reasons, not all of which will be shared by every person who posts like this but certainly many of which will overlap.
As a general rule, people like to have their opinions heard. You
like to have your opinions heard. It's human nature. They also like them to be heard by an audience familiar with the topic. It's also very much a human need to have one's opinions validated by finding others who agree. For a given game, the best way to do this is on fansites like this one.
Another reason is that most of the people who are complaining about the game don't want
to hate or dislike the game. They always intended to like the game. It is, after all, why they bought it and signed up to a site like this in the first place. Discussing reasons they in the end don't like it can be theownutic, it can be done in the hopes that things will be done to improve the game, and a variety of similar reasons.
It's also the case that many folks who don't play the game simply peak in on the forums every once in a while to see what is going on. Then, when they see a topic about which they have an opinion, they will post just as you might decide to post on a blog article you come across for no reason other than that you have an opinion on the matter. It doesn't mean that these people are coming to the site with the intention of complaining or bashing the game or convincing anyone of anything. Sometimes its as simple as seeing a discussion and saying, "Hey, I have something to add to this." This is especially true in a topic like this, where the original question was, "where has everyone gone?" It makes perfect
sense for those who have left (and are therefore contributing to the feeling that everyone has gone somewhere) to explain the reasons that they did.
Then there are of course those few who just like to be trolls and ruin others' fun. Yes, they are a part of it, but I think this is by far and away the least common reason for people posting "against the game" on a forum like this.