What is the word whose meaning is to "oversimplify a complex issue; often incorrectly?" [duplicate]

To dumb down something.

Dumbing down:

  • Become less intellectually challenging; OD
  • The act of taking a product and watering down elements of it to make it appeal to a broader mass market. This often damages or destroys the very elements that gave the product any appeal in the first place; UD

To trivialize is to make something seem less important or serious than it really is. It can be extended to mean "oversimplify".