There's a fun series of YouTube video essays called "The Whole Plate" that discusses film theory and critique through the lens of Michael Bay's "Transformers" movies. Pretty fascinating stuff, ranging from cinematography shop-talk (you can't remember what happened in a Bay movie because there are rules for holding audience attention and he breaks them on purpose to make you feel anxious) to critical lenses and how the same movie tells a different story depending on the preconceptions you bring in.

The author, Lindsay Ellis, uses Bay's work for a couple of reasons: she actually enjoys the films, they're pop-culture relevant so her target audience is likely to be familiar with them, they have been heavily criticized as having little artistic merit... and they grossed like $4 billion worldwide, so at some point the conversation of what art is becomes irrelevant if the guy doing it bought a mansion off the work.

(As you noted, any debate over the artistic merit of MLP and Discworld will reveal far more about the biases of the debaters than the works themselves, so what would be the point?)