I’ve seen mediocre content underperform because of poor SEO. I’ve even seen poor content peform middling-well because of proper SEO. But one thing I’ve never seen is truly great content fail to perfrom because of inattention to SEO.
SEO is not magic. It’s just one set of many content quality signals search engines consider. If you’re not investing in quality content, it makes little sense to invest in SEO to try to compensate for that.