When there’s so much money at stake, people will go to great lengths to reverse-engineer the things that put them higher in the page, no matter how you try to hide the levers that make the rankings work.
Instead, you want to throw queries and user behavior into a blackbox algo and have it tell you a result then give it feedback on whether the result was good (did the user come back and ask the same question? did they click the top result and leave or did they have to come back and click through many more?). I think this is kind of how google works now, though results are frequently meh. Millions of backlinks will get you noticed but your ranking will just keep dropping if users don't appear to find your content useful (e.g. they hit the back button a lot and keep searching).
What stops me from writing a bot to simulate that behaviour for my website (or websites of my competitors) ?
One form of personalization that they applied early on is move results you click on a lot up in your results you can’t trust the serps you see at all.
They also inject a lot of arbitrariness and randomness to make it impossible to make small changes to your site to incrementally improve it the way you would improve an advertising campaign. One reason the web seems so frozen is that if you have a successful site and make major changes to the layout, titles, link structure, etc. you will possibly trigger the ‘chaos monkey’ and wreck your ranking and it may never recover.
That just turns it into a statistical problem.
I don't think you can escape the problem of a search engine being used as an oracle.