Folks claiming a ride-sharing service as the end of GA aren't looking around very well. They aren't minding their surroundings. Not living in the moment. Whatever other Jedi cliche I can come up with.
GA is already dying folks. It is withering away, as pilots get older and fewer folks step in to fill the ranks. I don't think there is really that much you can do to hurt it at this point. My airport used to have a tie-down area that was full of airplanes when I started 15 years ago. They just bulldozed it. I'm told there are empty hangars as well. Hell I'm told, the one next to it has an aircraft frame in it and little else (unless you count motorcycles).
Yeah, this could get bad if pilots allow pressure from others to stop them from acting like pilots. I've done the ride share thing to the Show, I was PIC and made certain the guy knew it. Had a good time, I'd do it again.
Thing is, non pilots get in my airplane, they hear all about how dangerous GA is. They hear all about how I might turn around midway if I don't like what I see. They hear all about how we could wind up sleeping at our destination or driving home if I don't like what I see.
But half my flights are just me flying to fly going somewhere local for lunch. Give me pax and I might really do some travel. So long as pilots act like pilots, this will work fine. The minute someone caves to some mouthy passenger, we get problems.