Journalists, most kinds at least, are like teachers and government officials; they are public servants. It is simply not surprising that the best and the brightest are attracted to other professions which earn one greater respect and remuneration, e.g. the law, medicine, banking, and, for the time being, computers.
An election-based government operates in a cycle. Someone is elected, they do things, we hear about it, then we vote. This entire process breaks down, in generally tragic ways: if good people stop running, if we no longer hear about what they do with a critical eye, or if we stop voting. It is hard to imagine a government prevented from doing anything, but it is hypothetically possible. Journalism is how people have traditionally heard things about what is going on.
The media criticism business got its start, as far as I can tell, back with Reed Irvine and "Accuracy in Media." This was a John Birch Society friendly group which bashed the media for its pro-Democrat Party, soft-on-Communism stances back in the 1960s (UPDATE: It still exists even though Mr R Irvine died in November of 2004). I don't believe much of the criticism was valid, but I do believe there has always been an "establishment press" league of news outlets friendly to the administration. The Executive, Judicial and Legislature were all in the hands of Democrats at that time, so it is (regrettably) to be expected that a pronounced pro-Democrat bias existed in the news. Similarly, now the major TV outlets produce numerous pro-administration peices. For example, I am led to believe that, before the Iraq War, the number of pro-war interviewees on the networks and cable news shows numbered 800, while the number of anti-war interviewees numbered six.
Now Media Matters for America, and for a decade or more now FAIR illustrate on a regular basis the shoddy, pro-corporate, pro-Republican biases of the media.