Yes, general investing is not zero sum, however many methods of advanced trading are. Options trading, which is prominent and easy to access on Robinhood, is much closer to gambling (and is treated that way by many users) and is zero sum.

Most active trading strategies require successfully arbitraging, or extracting inefficiencies out of the market, and you can’t do either of those things without someone else losing money.

Passive investment is investing in the companies that underlay the market, active trading is extracting value out of the market itself.