Science literacy aims for a broad critical understanding of the nature of science and its role in society. I view science literacy as synonymous with "critical thinking about science", and included in this would be basic literacy in the history and philosophy of science.
A typical K-12 ➔ undergraduate ➔ postgraduate science education is not intended to produce scientifically literate citizens. This path is one of increasingly narrow specialization. The farther you go, the less exposed you are to science outside of your particular area of expertise.
This is not a failing of the system, because the system was never designed with science literacy mind. It was designed to cultivate and train a scientific and technological workforce that can support the economic goals of government and the marketplace. From this perspective the science education system can be judged a success.
But the result is that most people, even many people with PhDs in science, are for all practical purposes scientifically illiterate.
A critical thinker's library should have a couple of books on the nature of scientific reasoning. Everyone should know that scientific opinion is always open to revision in light of new evidence. Everyone should know what a randomized controlled study is and why they're important. Everyone should know how scientific results gain authority over time, as communities of scientists explore and eliminate alternative hypotheses and converge on results. And everyone should know something about the landscape of science, how different branches of science relate to one another.
But of course everyone does not know these things. We have a long way to go.