Ben Brantley on Michael Jacobs’ Broadway play “Impressionism,” starring Jeremy Irons and Joan Allen: “[E]ven if I were to back up all the way to the Hudson River, with half-open eyes fixed on the stage where Mr. Irons and Ms. Allen labor so valiantly, ‘Impressionism’ still wouldn’t look credible. I mean this both in terms of its plot and as a proposition that would entice some very talented people and a vast army of producers.”