@eob This is very true, and, I think, inevitable.
Our computer systems would fare much better if we built them with this realization, learning from past mistakes, but also integrating well with the "legacy" foundation they rest on.
Build open, extensible and resilient systems. One day your shiny new system will *be* the legacy system, and those building on it will either curse or praise it, depending on how well it can be adapted and integrated with.