I think code verbosity (which anyone can read and understand) is highly underestimated these days. I don't think writing less lines of code is any good if you need to explain to people what you did (yes, even smart people sometimes don't figure it out right away if they didn't use a similar library / concept before, and you don't always have smart people reading your code anyway, we all know that)

If you optimize your code to avoid any duplication, you are probably wasting more time writing / extending libraries, doing pull requests than getting working software done.

Refactoring, and good design is critical, helpful, almost mandatory, but if your feature is not out there on time because you over refactored / engineered your code, and some other startup get's it out there faster, no user will care.

users don't do view source before they pay you.