Instead of "headless", which I agree is confusing, perhaps instead: bare-bones; unstyled; fully customisable; extensible; unopinionated (maybe). "Artisan" seem

Instead of "headless", which I agree is confusing, perhaps instead: bare-bones; unstyled; fully customisable; extensible; unopinionated (maybe). "Artisan" seems fine, although it's slightly obscure. Perhaps instead: control-freak; obsessive; perfectionist. They are somewhat negative, but they're also points of pride for some. So for example: tiptap, the fully customisable editor for website perfectionists. Just some suggestions :)