Based on my experience and that anecdote, I think the lesson might well be that users of existing complex software hate any change. Maybe it was "hard to learn

Based on my experience and that anecdote, I think the lesson might well be that users of existing complex software hate any change. Maybe it was "hard to learn", but they had existing customers anyway despite that who found value of some kind, and their existing users have already not only already learned it enough to do what they need to do (and don't want to relearn anything, like all of us), but they fact that they have learned a complicated thing is a badge of honor and even (subconscious) job security. I'm not confident the whitespace or design goals were the issue, rather than any change at all -- I'm not even confident that _new_ users would have preferred the old design. Or if there was a really good design out there that would have worked better for most both new and existing users, which a skilled and experienced designer could have come up with after actually observing and talking to users and understanding their work well -- I'm still not confident in any conclusions about how much whitespace it would have had.