Computers, digital text, and digital information distribution/transportation have made writing and thoughts cheap. Arguably due to what we are surely all aware of, humans rarely value that which is cheap, whether monetarily or in effort and consequential qualities. What people seem reluctant or maybe unable to acknowledge is that predating the current AI Slop, was what could be called Human Slop, low quality, low effort, careless output that was cheap; regardless of whether AI slop now outperforms.
It is why you are justified in pointing out that even in the post complaining about AI Slop, the human has apparently abandoned what would have been common practice in just the recent past, using basic spellcheckers or simply reviewing what was written and also practicing with deliberation; the art and skill of writing, grammar, and sentence structure.
No one is perfect and that is also what makes anything human, somewhat inexplicable and random variation. However, it takes a certain refinement before unique human character becomes a positive quality and is not just humans being sloppy ... human slop.