Reviewing Andris Nelsons's first concerts as the music director of the Boston Symphony last fall, I wrote: "What Boston requires most from this hugely gifted, still maturing conductor is his full attention." With the announcement today that Nelsons will become the Kapellmeister of the Leipzig Gewandhaus in 2017, it's clear that Boston won't be getting it. I concur with the Twitter reaction of my New Yorker colleague Leo Carey: "Stars too powerful. Music needs wider pool of performers considered bankable. Orchestras need committed directors."