I don't see the hobby in bad shape at all.
What I see are great cars are still holding a tremendous value, original and NOS parts are now seeing the light of day since long time collectors are letting them go or passing on and their families are letting them go.
If you go to any show (when we're allowed to again), people may ask if your car is real, thats okay because when you say yes, their eyes get wide and they WOW. If its a replica, then they say man that is a beautiful car and guess what, you had a great conversation and possibly made a new friend.
I think a lot of times when we get older our perspective changes not because the hobby is dying but because we have shifted our focus. You have "been there and done that" so your enthusiasm to create a club, join events, create an event, call fellow enthusiasts and hang out, trade parts, buy parts etc... isn't what you do anymore because quite frankly, you changed. You don't need the parts, your car has been shown many times and received numerous awards. Your car is fussy, no AC or the AC doesn't work, not as comfortable as your new car that your lady wants to take to dinner.
I haven't been in the SAAC very long but I will tell you, if you put forth the effort to attend shows and get involved again, your opinion will change. Your crowd may change because most people in the 20's can't afford a 65-70 Shelby but they love their fox bodies or replicas. Engage them and see their excitement.
Heads up drag racing has made a comeback over the last 5 years, the venues are packed with people doing Friday night street fights, run what you brung type events. The auctions were packed with a lot of good cars going through them.
So ask yourself this "have I changed?" before you pass judgement or make a blanket statement that the hobby is dying. I bet you will say yes, you have changed, because you are not as involved in the hobby as you once were.