Yeah I think you're forgetting that consumers are a very important part of functioning local, national and global economies. If the only businessman in a farming town runs a grocery store selling the potatoes from one farmer and you killed everyone else off besides that farmer and store owner, that town's GDP will drop to 0 within their lifespan. This can basically be extrapolated to the global level?

Also why should we artificially extend forcing most humans into agency-less drudgery for 60% of their sentient healthy waking hours? I think the sooner we embrace having 15% of the population producing the net economic output and providing the rest of the society with what they need, the faster we can figure out a significantly better and fulfilling society for everyone.