What you have to understand about D3 is that it's MEANT TO BE REPLAYED. Beating it on Normal and saying "well that was stupid, this game sucks and it wasn't even hard" is kinda like watching porn just to see the furniture they're using. You're looking at all the wrong things! Not only do the dungeons have random layouts and mob spawns, but the step up in difficulty from Normal --> Nightmare --> Hell --> Inferno is ridiculous.
As far as it being a MMO v. Not a MMO: While it may not be massive, it does have an online community. You can join public games, or games with your friends. It has an auction house. It's everything that an MMO is, but it lacks the douchebags that would be butt fucking your stash or the BS/JC trainer (which is what I love the most about D3) because they got bored. All the fun, none of the headache in regards to dealing with people.