Complex sentence: Katzman's final films were marginal, and the assembly line production system that had served him so well now seemed out of step with the time, and for the first time, Katzman was unable to adapt to changing circumstances.
Split into simpler sentences: Katzman's final films were marginal, and the assembly line production system that had served him so well now seemed out of step with the time. For the first time, Katzman was unable to adapt to changing circumstances.