That's true for product development, but it's not true for mathy libraries. Perfect is achievable. For a released software that humans will decide to use or not, rapid iteration is great. But also: https://randomascii.wordpress.com/2014/01/27/theres-only-fou...

Precision and exactitude and formally proven correct software can exist in some problem domains, and it's kind of silly to not achieve that when it's achievable.