Alternate theory... a few months into the LLMism phenomenon, people are starting to copy the LLM writing style without realizing it :(
I just don't know what's supposed to be natural writing anymore. It's not in the books, disappears from the internet, what's left? Some old blogs for now maybe.
But luckily there's a large body of well written books/blogs/talks/speeches out there. Also anecdotally, I feel like a lot of the "bad writing" I see online these days is usually in the tech sphere.