I could make the same claim that you've made about pawn shops as a reductio ad absurdum. That individual with second hand jewellery gained X dollars when they sold it to the pawn shop and the pawn shop lost X dollars. So it's zero sum. Although it isn't except in the most myopic sense (that of dollars). Transactions (on financial markets or otherwise) are always subjectively positively sum in utility and that's what matters.
Here's some examples. Suppose someone gets a terminal illness and needs to sell all their stocks to a willing buyer in order to get cash. It's zero sum dollars (just like every material transaction in the economy) but utility was gained, the person that needed the liquidity got it immediately and with near zero slippage. Other examples: The farmer that needs to hedge their crop yields, the airliner that needs to hedge oil prices, the gold miner that needs to hedge gold prices. The supply side and demand side of this equation gains utility from engaging.
> "There are limited resources and society have decided that these people deserve a big chunk of that resources."
As if society decided collectively to pay an unfair amount to a good/lucky trader. They took it from other market participants and not from average joe. My intention with my initial comment was to point out that it simply doesn't matter if one market participant has 600 million more than before, because others in the market lost it.