I haven't been in the GA world for long. I always try to visit a new airfield everytime I fly (Leicester yesterday) and I usually find a fairly thriving scene; which suggests to me from what has been said that it used to be a lot more thriving than it is now, or I've just been lucky with my choice of airfields.
Flying has always been expensive, in real terms it's cheaper (for me) now than it would have been 40 years ago so I can't see the argument that it's being priced out of existence. I can't comment on over regulation as the regulations now are the same more or less as when I started so have nothing to compare it to.
Coming from the gliding world I'm happy to report that
AFAIK the gliding scene continues to thrive.