It is easy when writing in a hurry with something like NaNoWriMo to write sweeping generalizations and use stereotypes to describe characters and scenes. If it works and the character or scene is small, then use it, but NaNoWriMo is a word-count driven competition with yourself. Go beyond generalizations and stereotypes to flesh out your scenes and characters.
All villains aren’t evil. Some function within society with few noticing until something triggers their evil ways. Help us see past the stereotypes of an evil villain to see what they are really made of.
Not all heroes are here to save the day. Some go reluctantly such as antiheroes, the reluctant heroes that ambivalently thrust into conflict and onto the hero’s journey not of their own free will.
Not all butlers, maids, or shoe polishers are black. Not every car mechanic is Latino. Not every person shot by police is black. Not all rich people are white. Break with stereotypes and add life, texture, and passion to your characters by breaking the mold.
When you write with generalizations and stereotypes, you are often selling your characters short. Let them breathe into being with full hearts, souls, attitudes, and presence in your story. Peel away the layers to find what makes them unique and introduce that uniqueness to your readers so they can break through their own stereotypes and judgement calls.
Human beings are complex creatures. Sure, there are some characteristics and traits that most of us share across cultural and historical divides, but go deeper. Paint colorful pictures for your readers.