> Instead, the right train of thought is: "what would perfect code look like?"

That's the classic 2nd-system effect - "let's rewrite it from scratch, now that we know what we want". And you throw away all the hard-learned lessons.

https://en.wikipedia.org/wiki/Second-system_effect

Not really the case; you're misunderstanding the term second system effect.

    > The general tendency is to over-design the second system, using all the ideas and frills that were cautiously sidetracked on the first one.  The result, as Ovid says is a "big pile".  For example, consider the IBM 709 architecture, later embodied in the 7090.  This is an upgrade, a second system for the very successful and clean 704.  The operation set is so rich and profuse that only about half of it was regularly used.  (p.55)
    > 
    > The second-system effect has another manifestation somewhat different from pure functional embellishment.  That is a tendency to refine techniques whose very existence has been made obsolete by changes in basic system assumptions. (p.56)  

Suggest that you re-read what Brooks meant by "second system effect".