All the software anyone needs has already been written.
I would bet that 99.9% of software that people will need in the next 100 years and could get utility from has not yet been written. Not to mention upgrades to the software that currently does exist, and is pretty crappy.
I took me back to last week when my Internet was down for 24 hours and I felt so helpless. All my devices useless. My iPad, my smartphone, my smart TV, my laptop... expensive decorations.
That is strange - all of those things work for me even if I have no internet.
Interchangeable parts won't.