I'm assuming the post was written by somebody who doesn't have an English Lit degree. They seem to be confusing two different things that sometimes overlap: Metaphor and Subtext.
Sometimes a writer deliberately puts subtext into their work, usually this is in the form of metaphors, where something in the story actually represents something else. If this is not strongly pointed out or even alluded to by the narration or directly discussed by the characters, it's a form of subtext.
However! Subtextual meaning still exists when unintended. For example, you might say that Batman is an implicit endorsement of western authoritarianism and cultural dominance, being a story about a straight cis white American man with lots of money who is stacked with muscles like a classical god and dressed in a costume that is a sort of symbolic nudity, and a cloak (a symbol of rulership) who is celebrated for freely blasting his way around the city in his powerful muscle car hitting people who refuse to conform, often due to mental illness, and is attractive to every woman he meets.
This is almost certainly not intentional subtext. But that doesn't mean that it's an invalid thing for a literary critic to say, or should simply be dismissed. Acknowledging this as a valid way to read batman can tell you a lot about the people who are obsessed with him and how he's remained one of the most popular characters in the world for decades. It might also make you a better writer if you can think in such an objective, abstract way about deliberate versus unintended subtext and how your work could be read.
The entire point of literary study is to understand ourselves, humans, through texts. What we deliberately say about our desires, hopes and fears... and what we might say involuntarily. Was Dracula intended to reflect the fears of strangers from countries we knew little about coming over and destroying the purity of our English women? Or is that an element of unintended subtext? Are classic Disney villains often coded gay in their appearance and affect deliberately to demonise homosexuality, or is it an accident of cinematic tradition based on much older homophobic tropes used unthinkingly, or perhaps a reflection of subconscious fears and biases the creators of those movies might have had?
It's fine to just enjoy something for fun because it's fun. I'm not going to rain on your parade if you like... I dunno... Sword Art Online or something, but if you're studying something in English Literature... well, the whole point is to find things to discuss, and if you can't find anything to discuss about a text, whether the author intended it or not.... you're not looking hard enough.