I’ve always had a sophisticated vocabulary, now people think my content is AI generated. Frown.

Vocabulary is only part of it. LLM style is pretty recognizable, and most people don’t normally write like that. One reason is because they’re trained in a lot of marketing material, news articles, and the like. If it sounds like a self-unaware middle manager writing on LinkedIn, but it isn’t one, it’s probably an LLM.