Art should have a larger, deeper, more important message than simply " That's Beautiful!". Great art has a multi dimensional message that reaches past the average, past the mundane and past simply beautiful, it should instead speak on multiple levels. Frankly I have often thought of the "Its Beautiful" critique as sort of an insult. It is like they were comparing your work to the countless trite postcard and calendar images we are fed daily, pretend art produced in the millions to feed the masses, pretty boring and mundane stuff.
Beauty has its place, but artists should try to achieve more than simply create pretty pictures. Art should push the viewer out of their comfortable box, it should challenge them to think in new directions, suck them into different ideas and ways of viewing the world, wake them up from their indifference. The world is filled with beautiful pretty pictures, why not try to do something no one else has ever done or say something than no one else has ever said. This is of course much easier to write about than do but heck to not even try, to just fall in line with the others and do what they have done countless times before, where is the beauty in that?