It is amusing that your argument for software not needing “maintenance” is pointing out 3 pieces of software that had each received 20 years of maintenance by the time they reached the year you picked, 2003.
If you don't understand Excel's history, it's better to not make such a bizarre claim.
What part of my claim is bizarre? My claim is simply that Word and Excel had 20 years of history prior to the 2003 release. Your claim that it was originally written on a different OS is not really a reasonable counter-argument. The Windows version of Excel came out 2 years after the Mac version, so that only knocks the history of the "Windows" version down to 16 years.
And that those were in turn based on the ideas of Von Neuman & co. from 1945 of tabulating numbers efficiently, and so on and so forth in roughly equivalent leaps all the way back to the first abacus.
It's so reductive of a perspective that it's self-defeating, since no human being, including you, could ever actually comprehend the entirety of technological development, or even just the post-1945 developments.
I think it is a pretty clear line between attributing the quality of a piece of software to two decades of prior development at the same company, with its own continuity of developers and institutional knowledge, as opposed to the general benefits all software gains from the industry advances it builds upon.