> besides for training future models, is this really such a big deal? most of the AI-gened text content is just replacing content-farm SEO-spam anyway.

Yes, it is because of the other side of the coin. If you are writing human-generated, curated content, previously you would just do it in your small patch of Internet, and probably SEs (Google...) will pick it up anyway because it was good quality content. You just didn't care about SEO-driven shit anyway. Now you nicely hand-written content is going to be fed into LLM training and it's going to be used - whatever you want it or not - in the next generation of AI slop content.