I guess the improvements have been relative along with most other classes, new manufacturing materials and techniques, improved sail designs and maximizing the bouyancy whilst still staying inside the rules and template boundaries. The Mozzie of the 70's is a long way from where we are today but I suppose you could say that of many restricted class designs. If we didn't embrace new technologies we would all be sailing heavy "dinosaurs".
Hang on !! I've got one of the 70s designs in the back yard waiting for a new deck.

The bigtop Mozzie was trialed a few years ago but rejected by the assocaition for various reasons.