Things were easy until the mid to late 19th century. Anything could be produced in a carpenter, blacksmith or watchmaker's workshop. Lenses were ground, metals were machined, ...etc.
Then in the early 20th century things started to get far more specialized. By the mid 20th century, we had the transistor then the integrated circuit.
Now, everthing from ubiquitous phones to home appliances to street lights have complicated integrated circuits, CPUs, RAM, ...etc. that can only be designed by specialized teams, and fabricated in very high tech fabs.
I wrote about it here : Information readability and longevity in the digital age.