Well, the plumbing/HVAC trades pretty much went that way years ago. Plug 'n play domestic water manifold systems, with PEX tubing, no soldering required, just a plastic pipe cutter, and cans of glue/primer, flex duct, ductboard, used to have to buy a toilet, sink, or gas furnace thru a contractor, but the box stores/online sales changed that, but a lot of work remains to be had, rehabs of older homes, radiant/geothermal systems, electric radiant heat, and general service work. Today's younger folk have very few if any trade abilities, so there will always be work, and the shortage of skilled help.