MMORPGs are games that should require and thrive on a large number of concurrent players. In order to keep players logged in, the game needs to go one of two routes: Massive numbers that ensure that the servers seem busy even if everyone plays only 15 minutes a day; or requiring existing hardcore players to play the game for long stretches in order to the get the kind of rewards that hardcore gamers love.
Clearly the casual market is the easiest market into which to grow an MMORPG playerbase. Being casual-friendly is not far from "going mainstream" and "selling out", though. Casuals are generally non-gamers--in order to appeal to them, game designers need to assume less and less knowledge is at the disposal of a new player.
A designer can take two paths here. The hard and "right" path: he can do his best to design the game well by keeping mechanics simple but deep and by designing interfaces that are easy to learn but powerful. The other path--the "easy" one--involves stringing together the cheapest, most addictive proven gameplay mechanics on the market and wrapping them up in an inoffensive and relatable shell, replete with social tie-ins and micro-transaction money sinks.
Casual players will not have developed tastes in gaming. Cheap tricks can keep naive players entertained for a surprisingly long time. The number of naive players is so high that even if a naive player gets bored of a cheap hook within a few days or a month, there are enough naive players around to cycle through the system that there won't be much of an issue making more sales and keeping servers busy.
Regressive design preys on the naive casual gamer. We see this with the retro game resurgence--new generations of players are growing up in a world where their first game experience is in a 3D, multi-ten-million-dollar blockbuster game like Halo, Modern Warfare 2, or Mass Effect; game mechanics ancient, tired, and overdone in the eyes of experienced older gamers are novelties to the younger generation. They will play these games and give a market for the regressive and inferior. Of course some games can do justice to the old ideas, but most--as is the case in almost every arena--such games are crap.
Recycling the same tricks in better wrapping seems to make plenty of money. This is disheartening to me as someone who cares about games and enjoys seeing game design evolve towards radical new directions.
MMORPG design is falling into the same degenerative pattern that players of MMORPGs fall victim to: always taking the path of least resistance at the cost of long-term fun and success. It's worse in MMORPGs than it is in other genres, though, because the cost of putting an MMORPG together and running it dwarf the same kinds of costs for other games. And players have come to expect ridiculous amounts of polish and content from each new MMORPG. Expectations are in the wrong directions and far outreach almost every single development team's capabilities.
Where do we go from here?
To players: I'd suggest leaving the MMORPG scene and finding better games to entertain you. Or just stick to a polished and successful game like World of Warcraft or Lord of the Rings Online or enjoy a niche game that suits you like EVE, Darkfall, or A Tale in the Desert. Give games with alternate payment models (not F2P or P2P) a shot--like Guild Wars 2 (are there others?). Don't waste your time and money playing games that seek to exploit you instead of provide you with consistent fun.
To developers: Ditch the approaches where success will cost you upwards of tens or hundreds of millions of dollars. Make smaller, well-crafted games. Try new things on the cheap. Try different business models: don't fall into the micro-transaction conflict of interests and don't try to charge subscriptions which encourage artificial content extension. Or maybe just give up on MMORPGs all together and try to branch out into a different kind of MMO that may have a better market at the moment.