Technically yes it is. The problem with marketing it as such is all of the preconceived assumptions that people make about that term. Skill stats, XP points, leveling up, "grinding", D&D game system with "dice rolls" and cool downs, guilds, crafting, chat channels, 3rd person view and so on...
People who enjoy MMOs would then consider ED to be "broken" because it doesn't have these gameplay mechanics and people who don't enjoy MMOs wouldn't give it a chance.
It's just better to say that the game is multiplayer with a shared galaxy and let it speak for itself in terms of how it actually works and plays.