> not everyone can be an owner

Anyone with $10 and a phone can be an owner of the means of production (by buying stock).

> It's meaningless to say

The meaning is the massive improvement in the standard of living due to free markets.

BTW, if being "poor" means being in the bottom quintile of income, there will always be "poor" people, regardless of how well they live.

That's like saying anyone with legs can be a professional runner. In theory yes, but not in practice, not in a meaningful way.

Defining poverty as bottom quintile is also useless, yes. Defining poverty by comparing to the average or median income is the most useful definition. Someone earning less than half of average, for example. That tells you how well they can afford the limited resources of any society, as those track the average purchasing power.