Overshadowed by Controversy: While the serials did establish aspects of the Batman mythos that are still around today, such as the current appearance of Alfred and the Batcave, nowadays they are more infamous for their WWII-era anti-Japanese propaganda and racism than anything else.
Values Dissonance: Due to the films being made around World War II, when anti-Japanese sentiment was at an all-time high, the serials have quite a bit of an anti-Japanese bent to them, with the main villain, Dr. Daka, being a villainous Yellow Peril stereotype played by a white actor in yellowface. Needless to say, even those who otherwise enjoy the serials for what they are can agree they have not aged well in this aspect.
Narrator: This was part of a foreign land, transplanted bodily to America, and known as Little Tokyo. Since a wise government rounded up the shifty-eyed Japs, it's become virtually a ghost street.
Robin also tells Daka "You're as yellow as your skin!"