It's considered black hat because Google said it's black hat.
We're all playing in their playground.
If you're going to use it, do a LOT of human editing on it. My 2 cents.
At work, we trained an AI to recognize 50% of AI-spun content in less than 24 hours. (This was pre GPT3 though... ) After a month of machine learning, we were able to identify nearly 80% of it.
I have no direct / inside knowledge, but I'm pretty sure Google can spot spun content at close to 100% of the time. Of course, no one knows how much testing they do during a standard crawl. Analyzing content is expensive from a processing perspective.
That being said, you can probably get away with it over the short-term if you have no long-term revenue ambitions, and you're prepared to consistently produce new content to new domains. (Cue the guy who says he's been doing it for a year already. Yeah, yeah I know. Falling from a 20 story building is 100% harmless before you splat.)