I think the important part here is "from scratch". Typically when you're designing a new (second, third, whatever) system to replace the old one you actually take the good and the bad parts of the previous design into account, so it's no longer from scratch. That's what allows it to succeed (at least in my experience it usually did).

This is often quoted, but I wonder whether it's actually strictly true, at least if you keep to a reasonable definition of "works". It's certainly not true in mechanical engineering.

People misinterpret this and think they can incrementally build a skyscraper out of a shed.

Ah, the Second System Effect, and the lesson learned from it.

So true.

Came here to add this very comment. https://en.wikipedia.org/wiki/John_Gall_(author)#Gall's_law