I wasn't planning to write about Ballet Nacional de Cuba, performing this week at the Brooklyn Academy of Music. In fact, I was relieved that I didn't have to. How can you evaluate a company so storied? Its founder, the incomparable Alica Alonso, is already enshrined in the ballet canon. It is rabidly adored by its Cuban fans. It has catapulted so many spectacular Cuban dancers--Carlos Acosta, Jose Manuel Carreño, Lorna and Lorena Feijóo--into the international spotlight. The weight of its reputation, I thought, is too crushing; there isn't any room for objective analysis.