Complex sentence: Despite the competition, naysayers tend to overlook the financial success of the movie and deem it a flop, which is inaccurate and is thus seen, unfairly, as the turning point where the series went into decline.
Split into simpler sentences: Despite the competition, naysayers tend to overlook the financial success of the movie and deem it a flop. It is generally seen as the turning point where the series went into decline.