Has anyone actually succeeded in renovating their hard rock clay soil to a nice soft lawn without chemicals?

I've been aerating and spreading compost for about three years now and it seems my lawn is still rock hard, when it's really dry the cracks can be very deep and wide. I've also been using corn gluten meal for pre emergent weeds and fertilizer. Is there something else I should be doing? How long does it take to see improvements?

DH is ready to start spreading chemicals again, oh no!