Yeah, I consider complaining about academic writing like this to be just as curmudgeonly. I remember when I first got access to a good university library and could read all the criticism written about books and authors I had read – knowing that people like Watterson, Gene Wolfe, or Victor Davis Hanson had tarred it – and I found the vast majority to actually be valid and insightful, giving me an expanded appreciation of the book or an understanding of its place in the greater social discourse.
Yes, literary criticism often focuses on highly specialized concerns and not everyone is interested in e.g. queer perspectives, but can't we be happy that it exists for those who do want to read it?
I took this as more as poking fun at Calvin's common theme of superficially imitating "high art", opaque writing styles, and so on, in a very self-aware or cynical way, as a grift, since that's just what Calvin always does -- E.g. in the comics where Calvin sets up a lemonade stand, it superficially imitates a business, but is really just a scam.
An alternative or additional interpretation of his "curmudgeonliness" would be these are intended to tie into his bigger theme of critiquing those who gate-keep "high art". It's been a long time since I read any of these, but I do remember his biggest bone to pick wasn't with abstract art or anything in particular, but with the perception that comics / "graphic novels" could never be considered "high art". So, having his kid scribble some nonsense and call it "high art" is a bit of a middle-finger to art critics who relegate his work to the "funny papers"
As bizarre as this sounds, I actually do think there are legitimate criticisms of the mid-century abstract art movement -- notably, the CIA's involvement. However, that is pretty off-topic here and I highly doubt that Watterson has ever made a reference to this!
Edit: I'm not necessarily even disagreeing you, I think all of this can be true at once
Yes, literary criticism often focuses on highly specialized concerns and not everyone is interested in e.g. queer perspectives, but can't we be happy that it exists for those who do want to read it?