Then the 'way forward' is clear: Put every airport in Class G, to reduce costs and increase convenience.
Well Melbourne operated as a CTAF this morning and no one crashed...
Maybe your suggestion has merit, but the reality is that controlled airspace is supposed to coordinate the traffic, not curb the amount, it's just our current systems make it extremely inefficient due to cost cutting mostly. If the class Ds had the facilities and staff to coordinate the traffic it would almost work. However the airservices version of a class D 'service' is one controller, no radar and some silly stars and sids that make no sense and nobody uses.