The Met has opened this season with a slightly belated acknowledgement that a lot of blackface is not a good look for a big mainstream American institution. Unfortunately the resulting pale production of Otello, which opened on Monday and I saw on Thursday, doesn’t have anything else new to say. The production does, however, have a major selling point, one that hasn’t been nearly as widely discussed: Yannick Nézet-Séguin’s electrifying conducting.