having a single coherent thought about an established subject isn't really all that much to ask for.

A random reader on the internet does not owe you anything at all. No, not even a coherent thought. "I read this fic and it sucked" is a perfectly valid expression of feelings. I don't owe it to anyone to specify what fic I'm talking about - in fact, in non-anon circles, it'd usually be considered impolite.