And so when I take all those accomplishments together it starts look like post-modernism acts as a meta-critic for the practices or structure of various fields. Does this sound right?

It sounds like the ideal of what it should be. I think it's got some usefulness in this direction. But even when I defend PM as not being 100% bullshit, I have to take care to note that it's 99% bullshit. A lot of it is academic performance art.