The major problem with MMORPGs is that people who really shouldn't be playing MMORPGs are playing them.

The basic idea behind an MMORPG is that it allows players to ROLE PLAY. Take on the persona of, for example, a fantasy character and direct them through a world in which they can interact in that method. You know, the kind of thing people have been doing with D&D for decades.

Unfortunately, MMORPGs generally lack the people who really do want to roleplay, as well as an intuitive system that allows for the flexibility to do more than just go out and slaughter monsters. That is really their ultimate failing.