There are two basic kinds of game players; those for whom the most important aspect of the game is winning, and those for whom the most important aspect of the game is playing. For the former, the end-game is **the** destination; for the latter, the journey and not some final goal is the most important.
One might also very loosely define the first category as hardcore players, and the latter as casuals. For those whom winning is the most important thing, getting there first or among the first "means", to them, that they win. Burning through any new content first is, to them, the major goal of playing any MMORPG. These hardcore players tend to be much more focused and involved in the game, and in talking about the game, and in populating forums about their game, than casuals. This focus on the game leads them to take positions in the industry; hardcore players tend to become the developers and the fan-site gatekeepers of the industry. The hardcore treats gaming like a career; the casual treats the game like a hobby, and so the former tends to drive the functional path of the genre as it develops, because theyr'e the ones that end up in positions to make decisions about the structure of future games.
The hardcores brought an energy and enthusiasm into a genre that quickly exploded in popularity, but then hit what appeared to be customer base wall a couple of years after World of Warcraft was launched. Although many millions of people play games online, like hearts or poker at community sites, those people were not gravitating towards online MMORPGs. It quickly became apparent that online MMOGs were competing for the same base of players. After World of Warcraft, few new players were being lured into the western MMORPG market.
The reason for this is simple; virtually all MMORPGs are essentially the same game with various minor tweaks here and there, like better graphics, more character customization, wings, pets, real-money stores, pvp, etc. Since the bulk of western developers were culled from the powergamer mold, they essentially all think alike, and basically perfected their powergamer-oriented game with World of Warcraft.
Now, some may argue that WoW is not a true powergamer game, but here's my perspective: the powergamer developers built and revised WoW over the years around a fairly simple maxim: alienate as few powergamers as possible while appealing to as many casuals as possible thereby maximizing profitability. Second to that is: throw in whatever other games offer that seem to appeal to significant players if possible so that WoW players don't have to leave WoW to get the "stufff" the other game offers.
The reason new MMORPGs can't compete with WoW when it comes to size of player base is simple: all those other games are simply revised versions of WoW. They offer no significant reason to start over or go to a game that might fail and be a waste of money, when playing in Azeroth is money in the bank.
So, why do developers keep trying to sell us on WoW variations instead of trying something fundamentally different? Why do we literally have hundreds of MMORPGs out there and maybe one or two is functionally different from WoW? Is it because they wish to copy WoW's success?
No, the simple fact is that virtually all developers and idea men that gain entrance into the arena of game development must go through the same gatekeeping process, which means they have to be powergamers and have a powergamer mentality, which in turn means that they can only imagine games that are WoW-like; roles that fulfill group functions, groups that have access to content that can't be accomplished solo; raids that can accomplish content that can't be achieved by groups; a linear path of progression towards a guild-raiding end-game comprised of exclusively superior rewards and content, all centered around career-level investments of online time.
To the powergamer, this is what an MMORPG "means", and playing the game any other way, or for any other reason, is so alien to their thought process they can only muster contempt and ridicule for anyone that talks about offline progression or equitable solo rewards.
The powergamers that brought the necessary energy and commitment to the MMORPG genre to get it started have become the entrenched system, guarding the gateways and pumping out one failed attempt to draw customers away from WoW after another, becoming so desperate that they even offer their games for free. That has worked to some extent, but it is pushing the game industry into a certain business model that a lot of gamers abhor: the cash shop. It's hard to call a game with a cash shop a game, isn't it? It would be like Green Bay buying yards in the middle of a football game.
And so the MMORPG genre is stalled out, not because there is no more room for new, different, successful games, but because the powergamer oligarchy cannot imagine outside of their theme-park, linear progression, end-game, group-oriented,online- time-centric box. If they could, then we'd have true sandbox games, classless models, solo-oriented games, and offline progresion models ... but the fact is that we don't, and the reason we don't is simply because the developers as a whole can't fathom that people unlike them would play a game for reasons entirely foreign to their mentality.