“UML is the worst thing to ever happen to MDD.” Why?

Question

William Cook in a tweet wrote that:

"UML is the worst thing to ever happen to MDD. Fortunately many people now realize this ..."

I would like to know the reasoning behind that claim (apparently, I'm not referring to his personal opinion).

I've noticed that many people out there don't like UML that much. Also it is worth mentioning that he is in academia, where UML is preety much the holy grail of effective design and modelling.