If there is some group of N companies competing for some keyword, starting from the same 'lower quality' web sites, and they all do the same 'good' SEO stuff, then they'll all be right where they started again in terms of rankings, very likely. It's an arms race.

Competing for a ranking is pretty much a zero-sum game because no matter how much money you sink into it, only one can come out on top.

Compare and contrast with actually building stuff that makes people's lives better: there's still some competition, and winners and losers, but it's usually not a zero-sum game at all.