GA is suffering like many other sports and pastimes. One of the culprits is the PlayStation and its ilk, as suggested by wsmempson above. We are offered instant gratification (but not satisfaction) by modern life. Cinema, theme parks, YouTube all give you a thrill with no effort. But the way GA is set up means it requires a great deal of input before you obtain much in the way of satisfaction. I still remember when I was initially learning to glide. There was so much going on that I didn't have time to enjoy it. Sports requiring the development of skills and techniques before you can participate will also be suffering from the same problems. Yet those that allow you progress at your own pace are doing well, like cycling.
So if GA is to survive, it will have to find a way of giving satisfaction in the early days. Then once you have people enjoying what they are doing, they might be be prepared to put more into it.
PM