I haven't seen the A-S thread. But it's not just the racing -- it's sailing in general. The decline is inter-related, but I will try to keep the comments specific to racing.
I disagree that it's the "boring" factor. Racing is actually a blast, not so much to watch, but to participate in. The fact that it is not a spectator sport is one aspect that makes racing so much fun to engage in.
Because it's a "participation" sport, it's like being part of an exclusive club, or secret society if you will. There is an immense exhilaration and adrenaline rush that is hard to achieve elsewhere, made more special by the knowledge that our land-bound brethren can never understand it. Successfully executing a port-pole-starboard-set of the spinnaker at the crowded windward mark, then surfing it down to the leeward mark, peeling it, then snugging down smartly for the windward slog again -- it's hard to beat without bumping up to some of the seriously dangerous activities, like base jumping.
But you're right. It's in decline. And the primary reason in my opinion is the advent of "sport boats" and the costs associated with campaigning them successfully.
When I first got into it, the racing circuit was dominated by typical production boats of the "club racer" variety. These were boats that could be both competitively raced under various rating systems (PHRF, Portsmouth
, etc) AND comfortably cruised by a family. Pearsons, Catalinas, Beneteaus, various J-Boats, Frers, NYs, Rangers, Albergs, etc etc etc.
In days past, it was not uncommon to see some racers towing dinghies, particularly on the port-to-port or "destination" races. Folks sailed the sails they had, upgrading a single sail every couple years to both stay reasonably competitive and keep it affordable. Many of the crews were just families, or a bunch of friends out for fun and competition. The boats had decent accommodations, so staying overnight on the boats was pretty typical.
By the mid-90's or so, "sport boats" had very much arrived on scene. These designs took sailing to another level of speed and competition. No question, they are fun and fast to sail. But all that performance came at a big price -- and to stay competitive in these one-design fleets sails and other equipment need to be upgraded constantly.
It's like an arms race. Very expensive, constantly draining resources. And, increasingly, those without the unlimited resources simply turn away, with the knowledge that they don't have the big wallets and simply can't be competitive.
Also, unlike the club racers of yesteryear, the sport boats are minimally "accommodated", and as such they are no longer a destination unto themselves, but function simply as a platform to complete a race. They are not an inviting destination where a family or friends linger to commiserate about the race, or simply enjoy the camaraderie of fellow sailors and the innate satisfaction of being aboard a well-found vessel. They are a different breed of boat, a "let's get on and off quickly " sort. Something inherent and essential to the "sailing experience" is lost.
So it's been my general impression -- obviously not one I've worked hard to articulate given the lack of coherence here -- that sport boats and their ilk have been bad for racing and sailing in general. There are other factors in play, of course -- some more in the domain of "cruising" -- but that's a larger topic.