You need to understand the context. The quote in Gita was to motivate the best warrior of the time at the battlefront facing opponents who were mainly his cousins and uncles.
In that context the quote is about performing the duties you were born to do without overthinking the consequences.
the context makes it even worse. its a strange kind of tribalism that is being promoted here. "do what you are asked to without understanding the real consequences". btw war is actual zero sum usually.