Even without that, things can go really bad:

1. You're the only developer, then you burn out on the project.
2. You underbake the UI so much your project becomes infamous for how hard it is to use, complete with an elitist userbase that just screams "git gud" memes at everyone asking for help (most often happens to dev tools).

The rare occasion, it'll become like Krita, modern Blender, Audacity, etc.