I'm sure it's a bit of a cat and mouse game, the algorithm was designed to get accurate results, they can't just change it completely to avoid SEO abusers without losing out on real results too. And even if they did change it, SEO abusers would just change to match resulting in the same issue with worse non-abuser results.

For all of google's search issues, they're still the best search engine when it comes to results (outside of a few topics that are censored by google but not other search engines). I use DDG most of the time, but it's bing-powered results are just straight up worse most of the time, especially on technical or more complicated topics. The fact that Google is still the best search engine tells me they're not being lazy with their search algorithms, but that there's a bigger reason why they can't just filter out SEO abuse.