They've failed because of the nature of MMO's. MMO's, unlike other genres, are meant to be played in a perpetual state AND at the exclusion of other MMO's (Think about it, people RARELY play two MMO's at once.). Their specific nature makes their market a captive one, because population in game provides a huge number of benefits to the consumer playing the game. For example: If someone else were to make WoW, in almost the same way, with the same stuff, and even more content? It would still probably fail just due to the fact that more people play WoW, so more systems in WoW will work better thanks to more population (Dungeon Finder ect).
That social dynamic in MMO marketing is something most market researchers miss--but it's the core reason why this demographic is so hard to break. WoW didn't even break the paradigm. Sure a lot of us left EQ, but a vast majority of the population stayed (Hard to get precise numbers). WoW became a success by one means--it GREW the market. That's what a lot of these MMO designers do not get. You won't defeat WoW by going after the current market. You need to create a new market that will draw in people who aren't socially invested in WoW's systems.
Copying EQ isn't going to work, you're right. However, taking EQ and taking and iterating on it to correct the problems in a different way from WoW, just might create a new type of MMO that will grow the market again. And once the market grows, the population in the new game will have a chance to devour WoW--but that growth is essential. EQN, honestly, is the best shot I have seen for this--they are not looking to go after WoW's market. Those guys are looking to grow the MMO space again. They want OTHER sectors of the entertainment market, and it's a fantastic plan.