The "word of mouth" wasn't what broke the game; it was the people who had been playing it for years and years and years....that were bored out of their minds and wanted something new; they happened to make up most of the player base because people got hooked early and stayed out of loyalty; newer players had other games to choose from as the years went on so it didn't get as many new people in. No game can innovate forever. There are finite limits that are inherent to coding software and hardware. Think of the graphics of WoW; they could make the game look much more realistic and interesting, but it would take so much time, work and not even work on most computers after that as well. They can also only have so much data being transfered between computers and their servers because of the limits of the internet and hardware.
It's like the power grid in the US which I have heard equated to "a feeble old person". There is only so much it can do without failing. It would need a revolution in every aspect just like WoW would. That's why games like Everquest make sequels.

All game designers want everyone to experience the content also. You know why?

It's because the very design of an mmorpg is to be an rpg; the story is the most important part along with player communication and having fun(it still is a game).

Having elitism by letting some players have access to loot while others can't even get into the content to get it hinders player communication and, thus, destroys the mmo part of the mmorpg. That can kill a game fast.

Having content that only a small amount of players can see destroys the story and, thus, the rpg part of the mmorpg. People who can't do the content miss out on a huge chunk of the story which may be continued in the next expansion where they will be wondering "huh, that makes no sense". That can kill a game fast too.

Having content that is restrictive and challenges the upper echelon while frustrating or leaving out the majority destroys the fun of an mmorpg. Yes, some have fun by being challenged by everything, but if you can't see that they have catered to your elitism with hard modes then you are blind. Having no fun in a game will kill it faster than anything else.

Maybe you are blind Sylvok. You get catered to with hard modes, an exclusive boss and exclusive loot for all hard modes. You even get the challenge you want.
You say that "it's just the same content", but you don't realize that the entire game is the same content. There are only so many ways you can battle enemies. There are only a few mechanics to the whole game that really matter and can be summed up in one phrase: "kill them before they kill you and take their stuff".

They can't make hard mode "new content" because then it wouldn't be hard mode of the same boss; it would be a new boss or new place. They won't succeed by saying "this place is off limits to you losers" nor should they.

I bet you get angry at rich people for getting away with crimes and having life so easy, but the fact is your view about WoW is the same thing; if WoW really was how you claim it should be then everyone would hate you and the game. There would be no reason to play.

Games are an escape from reality. They are supposed to be fair, balanced and fun.

"The only thing one person can have that another can't is fun."
You obviously aren't having fun and even if you do have fun it won't last. The majority of people have fun though and will stay in the game for that reason. You'll likely quit because it's not your own exclusive club where you can be "holier than thou" to the rest.