There was once a time where a single man of average ability and intellect, given all required raw materials and written knowledge would be able to construct all the technology man possessed.
Towards the middle of the 20th century this was no longer the case, and by the end of the 20th century there were many individual technologies that were impossible. While a single man could craft all the items required for a steam engine, or an early automobile or a plane, with enough time and knowledge, in a single life time.
However the end of the 20th century saw such a vast wealth of new knowledge and most importantly its application in devices. It would take the expertise of a thousand human beings and the understanding of a hundred to construct a single device – of course with mass production those thousands could create millions of such devices. But it would still require those thousand to make one device or a million.
By the end of 26th century it would take the whole effort of humanity to produce the massive ships that sailed the skies, and the AIs produced technology as if they were a million Einsteins each in a single room, all communicating and debating. Mankind could never understand the devices they built again.