CNN is incompetent, Fox is usually reasonably competent at their jobs (when they're not hard-shilling conspiracy theories masquerading as news). CNN is biased, but Fox is straight up propaganda. The two aren't remotely comparable.
News media is contributing to the polarization for sure, but they're hardly the cause of it. Well, except for maybe Fox News and all the damage they've done to their viewers over the years. When folks who don't even watch the news know more about what's going on than those who regularly watch Fox News, there are bigger issues with the network and its reporting.