I am living in that country where poor people mine resources for others to live good, so I know what I am writing about. My family is from a mountain area where timber and cow farms were the only resources they lived on, now we can barely get enough wood for maintain the buildings because the demand is so big that we either limit the consumption or risk massive deforestation. Less people means less demand and more resources per capita.

That's only assuming that being able to buy cheap stuff actually makes people happier. I don't think it does.

Nobody is talking about happiness and nobody could agree with everybody on what that means. The word here was "better" and cheap labor in poor countries objectively makes our lives better, because we can afford more goods (both needed and unneeded) with our incomes and expectations regarding working conditions.

Whether we are talking about happiness or better-ness you are still projecting a value system and claiming it to be objective.

I personally don’t derive any sense of betterness from being able to afford more goods. I only see the ocean of plastic.