Seeing as I had already invested in converting our house to all LED I feel some empathy for your POV. In reality there are several problems in making it a modular design in the way you suggest: a unit that goes between your existing light fitting and "any old bulb" changes the dimension of your lighting set up (probably wouldn't look too smart having bulbs protruding from their cans), changing all your fittings would be even more expensive of course and that will deter many residential users, existing bulbs wouldn't work anyway as incandescents and halogen get too hot, the curly things really aren't dimmable and none of them have the ability to change the light color temperature.