Earlier quoted context omitted.
Competing against others to come out at the top _is_ useful labor. The best one wins usually and as a consumer you want the best products to come on top.
Maybe this is very Vulgar Marxist but that seems a bit like crediting gangsters competing to shake down construction businesses for building bridges.
Competition is why you have good products. Can you explain to me what incentivizes Apple to make functional and impressive iPhones instead of selling us barely working phones without cameras?