“For about two decades after the death in 1983 of the great choreographer George Balanchine, critics lamented the dearth of important new dance makers in classical ballet. … Then at the dawn of the 21st century came Christopher Wheeldon at the New York City Ballet, and Alexei Ratmansky at the Bolshoi Ballet. Suddenly ballets seemed to offer something fresh and new.” And they’re not by any means the only ones.