Edit: motohagiography, your post has been flagged, so I can't reply to you, but if you want to elaborate on your post, please feel free to use this as a jumping-off point.
You've made a big claim, I'm hoping you can back it up.
The ur-meme and ur-shitpost, which this ad is specifically looking for writers of, is that progressives cannot meme because they are humourless scolds and mirthless ideologues. This foundational meme about who does it well is propagated in forums that are defined by their problematic views.
The irony that this job ad would advantage people who not only traditionally hold this problematic view, but necessarily had experience exercising it via shitposting and doing it well, would seem to exclude people who hold progressive and radical values - yet calling it out is simultaneously offensive. The resulting paradox is what many people call humour. An actual job writing memes and quality shitposts effectively (if not explicitly) excludes the political left.
An example shitpost (which is the topic of the original post) addressing this specific original meme-about-memes was very much on topic, and amusing enough to share.