It's usually a refrain that comes as a leftist critique of liberals. Generally liberals believe that more thoughtful consumption can solve ills of capitalism while leftists do not. The same idea gets recycled without the critique to mean "nothing you do will reduce the harm you intend to reduce so you're doing that for no reason."

He means that nothing should exist, because life means death, existence means suffering. I honestly don't see the relation to capitalism because consumption is literally just spending for utility and consumption can be absolutely anything, it can be sustainable or not.