The irony comes in the last sentence: "Readers won’t put their fingers on what’s wrong, but they’ll sense that you’ve become artificially-flavored." The joke is

The irony comes in the last sentence: "Readers won’t put their fingers on what’s wrong, but they’ll sense that you’ve become artificially-flavored." The joke is that he wrote the preceding sentences in the paragraph in a way that intentionally plays up written-by-LLM-isms so that you feel the sense being described in the quoted sentence.