I think this statement is subjective and is the result of the class being much-maligned by Euro-centric gamers, who believe that the East Asian and European worlds need to be separate and mutually exclusive. The key is giving monks a reason to be there. Maybe in the Forgotten Realms today, there are monasteries being built…
As long as they keep adding classes and give players more than one way to engage the world, cookie-cutter classes are just fine. Too many people find out how to min/max anyway and variety is dead.
I would like to add my voice to those wishing we had new classes. The more, the better. Replaying old content with a new class is what keeps me coming back. I am particularly enamored of monks. I wouldn't mind variants of the current classes, either.