Given the way that Judy Garland was treated on set, this almost comes across as a tragic case of irony, but L. Frank Baum's original text was intended to define Dorothy as a feminist heroine. Written all the way back in 1900, had it been interpreted correctly it would have been considered almost revolutionary for its time.
When the book got the Hollywood treatment, certain clichés and tropes were bound to creep into it. The major one was casting Dorothy as the textbook damsel in distress, constantly afraid of the world around her and needing to be rescued by the male characters. By contrast, Dorothy is the one saving the others in the book, which also makes the important distinction that Oz isn't a dreamland, but a real place where women can be accepted as brave, strong leaders.