Grind, defined as the repetition of content, is necessary (a) because devs can't make new content faster than players can burn through it and (b) even if they could, that would lead to a situation where everyone was doing different things at different times, so finding people to do the content with would be near-impossible: Every new piece of content you add fragments your playerbase. Some games try to get around the former problem with user-generated content, but the quality is really variable, and anyway, that doesn't address the latter problem.

A better way to address this is parametrised (meaningful) variation in essentially the same content - procedurally generated quests. But if the variation is not meaningful, the procedural generation is for nothing, and people seem to be pretty stuck on how to make meaningful variation - at best it's cutting-edge research and far from being ready for commercial application (though it's basically what we were promised -- but didn't get -- in Skyrim).

I have played some "grindless" MMOs, and to be honest, I think they would make better single-player games (or perhaps small-scale co-op MP). They're actually diminished by being MMOs.