I agree with the direction the hobby is going. I think a big reason is in how our lives have changed in the last 40 years. We have so much less recreational time and father/son activities seem to declining as well. That father/son team is where I got my start as did many others. This not only meant trips to the flying field but many evenings and rainy weekends spending time together in the hobby room. The ARF and RTF models do allow many without the time for a full build to enjoy the hobby. Perhaps differently then we do but they are enjoying it none the less.
Yes, we haven’t a fraction of what we used to have but there us still a gold mine of old school kits and engines out there. In my own shop are a Webra Bully 35cc, a Webra Black head .61, an Enya .60X and a HB .40 PDP. All of those engines have kits or rebuilds waiting for them including a Pilot 1/3.5 Pitts, Spickler Quickie 500 and a Bridi Rearwin Speedster. With some patience I will eventually find a Miss Norway kit on either EBay or here. If not I can always scratch build one.
Point is there are plenty of options still available, they just take a little more effort to find then they used to. On the bright side, servos, batteries and radio gear in general is way better then what we had 30 years ago.