This is not (as) true of most other traditional media, e.g. local newspapers to the extent that they still exist. But cable news really is propaganda. Fox used to be the worst offender, but now they're all that bad, though playing for different teams of course.

There seems to be some kind of law that the larger a media outlet is, the more partisan it gets. Which is why social media is like the Exxon Valdez crashed into Deepwater Horizon and caught on fire.