I think we have done some complex systems well. Just not very many computer systems. It may be a consequence of computer systems being too pliable.

EDIT: Actually, before I forget, I heard a great aphorism the other day: When designing (distributed) computer systems, try designing it as if each "node" were an actual human. That'll usually ferret out most of the flaws in your reasoning. (No, it's obviously not foolproof, it's basically just a sanity check against assuming absolute reliability, etc. Kill cats. It's a rhetorical device meant to make you think. So think. Hey, do you own thinking. I can't think for all of you. Live your own lives!)