It seems that no matter the MMORPG, there are always complaints. They seem to be even more prevalent in MMORPGs than in most non-MMOs. The question that comes to mind is why? I can think of two good explanations.
The first, and most obvious, is that they have a longer life cycle than most non-MMORPGs. If a regular game is absolutely terrible, it may live on in infamy (like Duke Nukem Forever *shudder*) but most of the time, if you hate a game, or have problems with it, you trade it, or let it gather dust and move on. MMORPGs require more time investment, and that investment makes players more interested in their quality. If you think about it, a typical MMORPG costs about the same initially as a mainstream game, but the time investment is much greater. A mainstream game would be lauded as extensive if it contained nearly the amount of content hours that people plug into an MMO in the first month alone, and MMOs tend to develop over time, leading to even longer time investments (that and they are persistent worlds, so time investment means more). Because of this, players spend more time in the world, and notice more problems with it. In the Eve Online forum, someone referred to minor problems as one million papercuts...imagine what the major issues are...
The second explanation stems from the massively part of MMORPG. Mainstream games tend to play to a strength or two, attracting players from that sect and ignoring most others. Many games flop because they try to touch too many different genres, and MMORPGs cannot be an exception. Most MMORPGs try to appeal to as many people as possible. Because of this, they do not focus, but are thinly spread across the spectrum. An easy example of this is looking at PVP and PVE content. Some games, like Darkfall Online, have full PVP, while others, like WoW, focus primarily on PVE with PVP as a secondary layer underneath. IMHO, WoW doesn't do either PVE or PVP exceptionally well, which highlights the whole problem.
The difficulty is that these are systemic problems. An MMO focusing solely on one aspect of things to the exclusion of others will not have a large player base, and thus not be successful by most measures. Sad thing is, there's not a good way to fix this. This is why most people playing MMOs get tired of them after a period, and move on to the next one. If an MMO provided the best possible experience for them, they would not stop playing it. Many players are left having played all the available MMOs that appeal to them, tiring of them, and, given the lengthy development cycle of games, have nothing left to play. Hopefully someone smarter than me that works in game development will find a solution to this problem.