History says otherwise. The mass immigration to the US in the 1800s was all poor people arriving with nothing but a suitcase. They moved up into the middle class and beyond en masse.
Middle class people live better than medieval kings.
Even raising living standards for the poor through redistribution wouldn’t solve all our problems. Concentration of wealth is itself a net negative because it is concentration of power. Greater wealth concentration makes society more undemocratic, even if the bottom 50% were to become richer. Today billionaires have so much money that a group of them has gotten together to fund the abandonment of democracy in the US. They are largely succeeding. We are collapsing into “illiberal democracy” - a phenomenon that has been spreading across the globe in recent years. Our greatest problems, like climate change, worsen as wealthy interests prop up policies of denial rather than effective solutions.
A medieval king had political control. If society was heading in a direction that was going to harm them, they could do something about it. But members of the modern day middle class have virtually no political control. That is concentrated in the hands of the few and harms us all.
I'm sure you understand how capitalism works. If you do, you should understand that not everyone can be an owner, someone has to do the actual work.
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.
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.