Keyword stuffing dates back to when the sheer number of keywords on a page had a real effect on rankings, so pages would repeat a target term far beyond what natural writing calls for, sometimes hiding the extra repetitions from visitors entirely, stuffed into alt text, comments in the code, or text colored to match the background so it's invisible on the page but still readable by crawlers.
It doesn't work anymore. Search engine algorithms have grown sophisticated enough to read content the way a person would, judging relevance from context and natural language rather than counting keyword occurrences, which is exactly what made stuffing pointless as a tactic rather than just risky. Modern instances tend to be more subtle than the classic invisible-text version: a product description repeating the same exact phrase in every sentence, or a page that reads like it was written to hit a keyword quota rather than to actually explain anything. Both read as spam to current algorithms in roughly the same way the old invisible-text version did, and both risk the same outcome: rankings suppressed rather than helped.
