Sure, web search companies moved away from direct keyword matching to much more complex "semantics-adjacent" matching algorithms. But we don't have the counterfactual keyword-based Google search algorithm from 2000 on data from 2025 to claim that it's just search getting worse, or the problem simply getting much harder over time and Google failing to keep up with it.
In light of that, I'm much more inclined to believe that it's SEO spam becoming an industry that killed web search instead of companies "nerfing their own search engines".