Your supposition seems to be that media critique is worthless, the implication being that entertainment media doesn't have any effect or influence whatsosever on people that experience it. Proving a negative like that is basically impossible, for one thing.

Unless you're also going to claim that advertising in media has zero effect on people and therefore should not be analyzed or critiqued by leftists, that people would have bought those exact same products anyway whether or not those products were advertised to them, it is very presumptive to declare that people would act and believe exactly the same things and in exactly the same way whether or not they saw that same piece of media.

Would they have purchased the same merch of that entertainment if they didn't see it? Would they be comparing political figures and current events to MCU characters if they didn't see MCU movies? Unless your answer there is yes, there is clearly a non-zero effect that entertainment media has on people that experience it, for good or for ill.

That's what fictional media critique can (and should) focus on, if it's in a leftist space.

Uncle Tom's Cabin had a non-zero effect on the abolitionist movement leading up to the Civil War. The Jungle had a non-zero effect on the political momentum that then established the FDA. I would be dangerously naive to believe that Triumph of the Will, Birth of a Nation, or Mein Kampf had zero effect on the beliefs consequent actions of anyone experiencing them.

Implying that fiction is just entertainment and has zero effect on the world therefore leftists should not analyze or critique it seems like a longhand "don't say anything bad about things that entertain me."

It is possible to enjoy entertainment while tolerating criticism of that entertainment. I have problematic favorites too.