Hardly any of the content in the game is built to last, because of current mentality of play style. Which is: Get reward. Get out. It leaves a trail of dead content in its wake. The only reason people continue to grind content is for that same basic outcome (tomes), or because it offers something like experience. And the ones who don't care about having +20-25 ilevels on the (usually low) next requirement gear, wait until the new stuff comes. So they aren't grinding with the others. Making the content even more useless to them.
So as they investigate the trends in play styles, they see the majority of players are "content" with the current system. They see people will continue to grind out the same content to get "best loots" until they add something new. If that mentality stopped, there would have to be a new system. Because "best loots" or mount+1 wouldn't be rewarding enough anymore to grind out a couple of raids. This is why they have literally said that right now the current system/model is working.
"But that's how the game works!" you say. Only because the majority chooses to play it that way. The game is essentially an ilevel creep loot grab in its current state. People are better off playing something like Diablo 3, if that's all they care about. The rest grind and grind until they get a magical glowing dog, or some other mount that will be hidden away when the next one comes.
Others tend to like the offbeat content. Like Hildy, beast tribes, etc. It has a little story sometimes, and though it becomes "useless" eventually, it's different and fun to start with. Just like everything else that's new, it's an experience at first. Even if it is less rewarding, a lot of people like this type of "different" content. (And I use the term different, as opposed to grinding out dungeons.)
So yes, I can see the point of the OP. He doesn't think any of the content being added is worthwhile. It's because it won't be after awhile. Nothing in the game will be at a certain point. Even the ilevel creeping will be pointless when the game ends. Because there will be nothing to use that gear on at some point in time.
Threads like these usually never result in viable solutions to fixing the current structure of the game. It's much ado about nothing.