If you're uninformed, you're lacking the knowledge you need. Uninformed criticism isn't fair, because you don't have all the facts.
An uninformed complaint to a store manager about the dog you saw in the produce aisle may result in embarrassment and regret when you learn it was a guide dog assisting its blind owner. Whenever someone is missing vital information, they're uninformed. This adjective is often used interchangeably with "ignorant," so you might say, "Poor social studies education results in uninformed citizens."