Races like that one do not represent the pinnacle of racing in North America, rather it represents a typical "run what you brung" phrf club race. The beauty of races like that is that anyone CAN win, even the oldies. Any given boat can benefit from being on the right side of a big shift, fleet compression on a dying breeze, or other teams mistakes. It is not an indication of one boat's overall superiority, nor is it an indictment of modern technology. (Don't forget, even the old boats benefit from technological advancements in sail, rope, and hardware technologies.) I have been in races like that one where even a lowly San Juan 24 has won overall. I am sure that San Juan owner was happy to get the pickle dish, and his moment of fame, but was under no illusion that his boat was superior to the rest of the boats in the fleet.
The Hobie 33, like the Olson 30 I race on, is capable of getting onto a sustained plane in the right conditions, and when that happens, all bets are off, because any displacement boats, no matter how new and expensive are not going to win a drag race. In a well set up buoy race that advantage may be partially offset by.the upwind legs where the bigger faster rated boats may be able to stretch out enough to hold their lead off the wind.
The J24 owes it's success to good marketing and strong one design fleets. One design crews tend to be more polished and know how to get the most out of their boats. At the same time they have tended to have pretty soft ratings under phrF, since the vast majority race one design so their rating has not evolved as other boats have. They are NOT particularly good boats overall, they are good one design boats. If you compare them to their more modern replacements like the Melges 24 they are complete dogs!
I agree with some of what you say here, but the idea that the J24 has a soft PHRF rating is just not true. The same guys racing their a**es off in regional one design events are also sailing weds nights and other local PHRF events. J24s that do consistently well in PHRF are being sailed hard and sailed well. A rating of 168 is no gift, and with >5000 hulls sailing for over 30 years, it is one of the most well established ratings you could find.
I also think it is a mistake to compare the Melges 24 to the J24, they are completely different boats. If I traded the J for a Melges, my wife would never get on the boat again. You could not pay me to sit on the rail of a Melges 24, hanging over the lifelines by my midsection. They are fast and cool boats, but a completely different design criteria and set of requirements. I can not imagine anyone attempting to do the DTB race in a Melges 24, you might as well be doing it in a Hobie or Thistle. Aside from being boats that are popular to race and the same length, there is very little in common between them.
I don't know that there exists a boat which is "good overall", just ones that meet a set of design criteria and ones that fail to meet a set of design criteria.