In order to create an MMO you have to develop enough content to keep players busy for several months, if not indefinitely, in order to pay to keep servers running. It's impossible both logistically and economically to have a team large enough and with enough time to develop quality content at that scale, so the only option is to make a large amount of lack-luster content without putting much time into any of it. Even if you have the most fantastic combat system ever developed by mankind, no one will enjoy going through the same fights they mastered 10 hours ago, much less enjoy doing them for 500 hours or more.
Game developers are perfectly capable of making exciting combat, but no one will ever be able to do it in an MMO.






