From my experience greenfield /brownfield is not the best dichotomy here. I observed, how same tooling is generating meaningless slop on greenfield project and 10kLoC of change (leading to an outage) on existing project in one hands and building a fairly complex new project and fixing a long (years) standing bug with a two lines patch in the other.

And I have more examples, where I, personally, was on the both sides of the fence: defined by my level of the same problem understanding, not by the tooling.