The signal:noise ratio would certainly improve for anyone voting even if they didn’t use it to adjust other people’s search results.

I’m also skeptical that all of Google’s enormous investment in ML and staffing is completely powerless to identify bad actors with atypical usage patterns. What seems far more plausible is that they’ve decided it isn’t costing them more in ad sales than it brings in. There are individual domains which would improve results by being blocked but they also pay for search ads so … unsolved grand challenge of computer science it is!