If we give you $20 if art materials, we can't give Picasso those materials because you already have them.
The world is finite. Resources are finite, and infinite expansion is impossible.
Society is vastly more wealthy than we've ever been before. Access to education, medicine, information, transportation, entertainment are at all time highs. Life expectancies continue to rise and gdp adjusted by purchasing power on a per capita basis is up over 40% in the last 3 decades.
https://www.cnbc.com/amp/2017/02/22/us-life-expectancy-is-lo...
Either way, you shouldn't look too much at short term trends when trying to measure long term development. If you start from 1990, life expectancy has actually risen by 4 years.
If you were right, the $10 trillion China added to its economy annually (you know, just ~$64 trillion of new GDP that didn't exist before, over the next five years) - in just the span of ~16 years, would have had to come out of someone else's pocket, which would have caused extreme collapse in numerous other major economies to make room for it. That of course didn't happen at all, the rest of the globe's GDP expanded along with China in real terms.
For all realistic practical purposes - since we're nowhere near maximum resource utilization - that has yet to be an actual problem and we're up to 7.x billion people now. Every serious problem to that expansion, we've managed to solve, enabling continued expansion (see: we were all supposed to starve to death decades ago).
Back in reality - and out of the realm of theory that only exists in a strict vacuum - Capitalism is the exact opposite of a zero sum game. That has been proven by the radical improvement in living standards at the median for all the developed nations, all of which heavily utilize the free market economic system (including all of the Scandinavian nations, none of which are actually Socialist at all).
If Capitalism were a zero sum game, China would not have just enjoyed the greatest, fastest mass standard of living improvement in world history thanks to its modest adoption of the free market, and its blatant shift away from Statism.
The free market largely won globally, and thanks to that, the world has less poverty, war, violence and starvation than at any other time in history.
Is this true, though? Certainly as a percentage of global population things like poverty and hunger are in decline but some of this can be attributed to population increases. There were 795 million hungry people in 2015 [1], but this is more people than were alive in 1750. It stands to reason that 300 years ago there were considerably fewer individuals living on the brink of starvation.
[1] http://www.npr.org/sections/goatsandsoda/2015/06/01/41126502...
Software is a fine counterexample. It's made of bits, which cost nothing to create, and the value is in the order of the bits, not the bits themselves.