I've fixed our commercial (China quality) lasercutter using parts made on a cheap FDM 3d-printer. Fixed powertools like drills and drill-presses. Replaced parts on my bicycle. Made functional scissors, and a haircomb that I needed when no shop was open.

The issues are that for commodity items, in the first world, it is quicker to just buy them (if we don't have them already). They will also be prettier. Or if it is a custom item, one has to actually design&test, which is something that requires CAD skills and some hours of work. Teaching this will take some time.

Most people just watch kitten-videos and play Farmville using their Internet-enabled devices. Does not mean the devices are low-quality and cannot be used for useful things.