With the CIA, FBI, and other organizations I've worked for, you'd probably be right. The NSA is the only meritocracy that I've encountered in government work, although I only have a total of 10 years of experience so I haven't "seen it all" per se.
When you work for the NSA, you can take a managerial route or a technical route for promotion. This means that you can achieve the highest rank (GS/GG-15) being either a manager or just being good at your job.
I once wrote a report which countered reports that other people had written, resulting in some angry phone calls demanding me to redact my correct report so as to not make them look bad. I responded with a no to all of them, and when circumstances proved the validity of my analysis, I was rewarded for standing my ground and not punished.
All in all, the people working there on the whole cared about doing what is right, is what I found. In that light, NSA stood in stark contrast to the FBI culture of major bureaucracy and lazy/inefficient practices.
As an example of the culture, I learned to program at NSA because when I said I was interested they said, "Here's a book and some servers.".