> Maybe you should ask yourself why you believe that 1) access to resources and technology are "basically constantly rising"

Because people have and share ideas, and I was using that as a shorthand. Even if they aren't, if you completely strike that part -- my point remains completely untouched.

> why the relative difference in wealth today is more important than the (magical?) existence of a system were everyone has continually gotten more access to resources and technology

Because in the context of "Wealth is having economic power over the people around you.", that is the definition of wealth that is used. To quote a randomly picked one, emphasis mine:

"Large possessions; a comparative abundance of things"

> You are aware that the default state of humanity hasn't been one of continually increasing access to resources and technology?

There was no default "state", at least by the time you're talking about humans, we probably already learned from each other by observation. Sure, politics and wars and religion and feudal dynasties and whatever make bumps in the line, but generally it goes up. Once things get out, they're out, roughly speaking (that's the keyword here), and even in the animal kingdom.

And as I said, even if that's completely false, doesn't matter for the wider point about wealth, and that it can only buy you power over others if they have less of it.