I honestly believe the only way for a search engine to be as valuable as Google was years ago is to let human knowledge drive more decisions. Maybe closer in spirit to what a web app store would look like, or closer to the categorisation Yahoo did. Not to browse by category (though even that would be refreshing at this point), but to better select the most relevant search sources.
That is exactly the whole problem. SEO SPAM is a symptom. The problem, is that Google went all in on ML and AI. I've been exposed to ML and AI going back to the early 1990's. It always ends up the same, stale sterile outcomes.
Google can fix this by someone doing an intervention with Pichai and concincing him that we are several decades away, still, from any meaningful use of ML and AI, get back to making search good.
On a positive note, Google does work well today as a spell checker.