It's also important to look at WHY a design is extinct. In the case of something like the Goliath, the design wasn't made in wide numbers and after the loss of its factory was well on its way to extinction before new versions began production as part of Project Phoenix. On the other hand, the Von Rorhs was very specifically made to go extinct, with the DCMS making sure never to replace losses or produce new examples.
In both cases, production had entirely ceased, and losses were basically permanent. In the Goliath's case though, effort was put in by those who had the few survivors around to keep them running- same for other oddballs like the Shogun, Falcon, Grasshopper, etc., while no effort was given to saving designs like the Von Rorhs or Pulverizer.
Another factor is whether the design was sound enough to survive years of refits and repairs. Grasshoppers are tough to kill, and seem to be repaired easily enough to be back in the field eventually after all but the most severe damage. On the other hand, the Wakizashi was an excellent design by the record sheet stats, but apparently was difficult to repair and maintain, so that design's extinction likely is due less to combat losses and more to being what in aviation would be termed a 'hangar queen'.