How to play Mozart correctly?

So one of the music directors at my school is also a conductor for an orchestra as well. On his upcoming recital(I think) he's conducting a Mozart symphony, and he said he'd prefer some Romantic period stuff to the Mozart cuz he said Mozart was hard for him. Now I know musically, Mozart is hard, but is that why it's hard? Or is it something more? And to add to that, how do you play Mozart correctly then?