That last 1% sounds like a godawful lot of work. With this attitude, you can never call something "done", and I deeply hate this notion of "things that are never finished". Like "you are never done learning C++". It implies that everything you do will haunt you for the rest of your life, that everything you do is a liability, and that there is some moral code or obligation to developers to do things because it is convenient to other people.

This, together with the ever-increasing complexity of well, everything, and the increasing number of "things developers should know about X", together with the notion that developers should always work fulltime and learn in their own free time, is non-sustainable.

It's a painful fact that in this "modern" environment, we just can't build anything anymore. There have been three critical vulnerabilities just today (Downfall, TunnelCrack, Inception). If you make a website it's probably hundreds of kilobytes big and you get people whining over accessibility and how it breaks dark mode of version 23.42.23 of their obscure browser.

Have you ever noticed how productive people like Fabrice Bellard just don't care about that stuff? The last procent is just a trap to suck you into the tarpit of spending time on useless shit. Choose a stable target and reasonable feature set, release, and never touch your project again. Bliss.