I don't think the problem is with people wanting more, more than for 3 months in, there is a great lack of content left for players to do. Even if you've been super casual and only recently gotten to level 50, you're running the same 2 or 3 dungeons to grind gear, and will soon be starting on the 'whole' 4 end game raid bosses. Sure, you can level another job, or even a DoL/H, but this is solid grinding of a fraction of the content you've already experienced.
Now lets consider those players that 'went hard' and got a level 50 in 2 weeks and have done the limited endgame content for a couple of months. Hell, let's consider the 1.0 players that have had all the classes level 50 since release. Tell them to stop QQing about limited content, despite the fact that they are paying the same monthly fees as you.
Edit: For the sake of argument, obviously neither of these views are supported by everyone, but I hardly think it is 'unfair' for people to have been paying for 2-3 months and asking for more content, whatever situation they may be in. If people start losing interest in the game, is it their fault, SE's fault, or a combination of both?
I know plenty of people that only log in to raid and cap myth for the week. It is only a matter of time before they stop logging in at all.