So the only point you can use to compare the two is that classes have roles? That's always been true, it just wasn't codified. Are Rangers main healers or guys who protect the back line in D&D? No? They do damage? Ok.
The difference is, I think, that 4e classes were designed to the role, as opposed to other editions where classes were designed to theme, and roles just sorta happened as a result of that. It also lead to a narrowing of some classes. For example, fighters became a pure melee class (because that's where a tank needs to be), whereas a 3e fighter could be an archer, duelist, horse-based knight, or any of a number of other concepts. The archer concept, in turn, got moved to the ranger who lost their magic (weak as it was), because the new ranger was a Martial Striker, and Martial characters don't do magic. This made a lot of people not recognize classic classes anymore, and since classes were closely tied to roles and roles were the most MMO thing about 4e, that's what people blamed.
Another thing that lead people to read MMO into 4e was the adventure/encounter design, where a lot of effort was spent on setting up encounter locations, complete with starting locations of various enemies. That often felt video-gamey – maybe not MMO specifically, but video-gamey.