"holding governments to account" is rarely a function of classified information, it's typically revelation of some corruption that was found via some kind of investigative work -- and almost always via public documents, hence the importance of the FOIA.

When leaked classified documents show something highly troubling, like the Snowden leaks or Wikileaks, the government doubles down and does everything it can to punish those leakers to the maximum extent, which is not what a "healthy system" would do to a whistleblower exposing illegal or corrupt activity.

eh, not quite. The laws which protect secret information apply to everyone (it does require that you have reason to believe the information is secret, but it does not require that you have clearance). There are however quite powerful defenses considering the 1st amendment, especially for journalists (in other countries this often much less strong, though usually there's something analogous. For example the somewhat famous idea of signing the official secrets act in the UK doesn't mean anything except that the penalties for breaking it get more severe: you can still expect to be prosecuted under it if you are handed information marked as secret and then pass it on, unless you can succesfully argue that it is somehow in the public interest for it to be published).