They called the substance axiomatic and much of it depending on specific definitions of specific words.

Well... they sure think their argument is axiomatic.

I would say that the more important critique I have is of the reasoning style.

Critiquing the style of a persuasive essay makes a lot of sense to me, however, because it accurately points out a flaw that will make it less successful according to this specific reader.

I'd suggest that if a reader is less successful at grasping the crux of an essay due solely to the writing style, that merely points out a failing of the reader. Digesting essays of varying styles is an important skill that one needs as an academic. That skill needs to be fostered.

But this isn't an academic context; this is a substack essay published on the internet for some internet denizens to read. In this case it makes a lot of sense to ask whether or not the essay succeeds at being persuasive, in the way it makes sense to critique whether or not a speech is delivered well. A public speaker can make a great point, but if they vomit on themselves halfway through the point, it makes sense to go "well, maybe we should address to vomiting thing" instead of "disgust in someone's vomiting on themselves is a failure of the audience".

It’s a low-effort substack troll post, it’s not that complicated