A practical and affordable flying car? Yes, we seem to have missed the mark on that. But even if we hadn't, there are a lot of collateral obstacles to actually "putting one in every garage". For example, I know far too many people who should not be driving a car, let alone an aircraft.
Moon base? I think the obstacles were much more political than technological. It's been almost 44 years since the first maned Moon landing (and safe return on the first try). Politics shut that program down Realistically, we only did Skylab because we already had almost all the hardware needed - but NASA's engineers and contractors did it. If nothing else, I'm sure they could have successfully and safely landed a Saturn third stage on the Moon.
Implanting computers in/near our brains? We already have implanted devices to grant vision to the blind and we are making a lot of progress with using brain signals to control devices. Don't know about you, but I know some people who are already trying to volunteer for a brain implant. Maybe not all who now claim they want such an implant would actually go through with it, but I'm sure some of them really would. Not that I think this is a good idea, I just see politics as the main obstacle to this.