The truly insane thing is that Safari's original extension mechanism was close to the model used by other browsers, was more capable than the API that replaced

The truly insane thing is that Safari's original extension mechanism was close to the model used by other browsers, was more capable than the API that replaced it, and was totally free and open to develop for. Apple intentionally killed their small but growing extension ecosystem in favor of more-limited, native code, App Store-only extensions that require a yearly developer subscription to write.