In those other MMOs, doing the same thing over and over again is more entertaining compared to doing the same thing over and over again in FF14.
It's quite simple, really.
Which is why the developers have to design their new content with the following in mind -
#1) Make it involve strategy, since the more you have to think, the more involved you will be, and the more entertained you will be.
#2) Add some random elements to the content, or multiple paths, so that the play experience is not always exactly the same. That is the problem with leves - it is always exactly the same. There's no variety, and you are not rewarded for trying anything new.
YoshiP hinted that the new dungeons will have multiple methods of completion, so that is a good sign. They can take a hint from Diablo III and add random boss packs and quests, like as suggested in this thread: http://forum.square-enix.com/ffxiv/t...Dynamic-Erozea
#3) Make it involve teamwork and cooperation, since different combinations of real-live people bring different playstyles and experiences. This in turn multiplies the variety and the entertainment value of points #1 and #2.
#4) Introduce more content that involves player-to-player interaction and competition. For example, EVE Online has hardly any "traditional" content in the way of quests. Most of the entertainment from that game is derived by the player vs player component and the competition among players for land and resources. All the major storylines in the game are totally player-driven. The developers don't have to do a thing.
Now, FF14 can't really do the same thing, especially in light of the devs' stance on PvP. However, that doesn't mean they can't foster more player to player interaction and competition.
One of the ways players can compete is through achievements, timetrials, and leaderboards, as I demonstrated in this thread: http://forum.square-enix.com/ffxiv/t...632#post129632
It would take old content that no one is interested in anymore, and give new reason to do it again.
Another way PvP can be implemented is through mini-games unrelated to battle. This is what I suggested with the Triple Triad game here: http://forum.square-enix.com/ffxiv/t...ll=1#post16036