My first question would be, growth of the hobby or growth of the AMA. While many would think they are one and the same, they are not.
The AMA is foundering. But the hobby? Depending on ones perspective it could be said the hobby has experienced considerable growth in recent years. If you call it an "aeromodeling hobby", then I have to ask, what has the drone craze done to it?
Granted, these are not the traditional kits many of us grew up with though some are indeed from kits and scratch assembled. Nor do they have balsa wings or rubber motors or make the screaming sounds of a nitro 2 stroke. But, they do fly. They have added to the over all options for folks to enjoy something that does fly. Even if an individuals main purpose might be to take pictures.
Some aspects of the hobby are indeed suffering and may never come back as they were. People "assemble" a plane now and call it scale. Harrumph! Real kits have to now be made by the individual before they can build the model. And the cottage industries come and go as before but seem to go more than they come.
The hobby is changing but I don't believe it's ready to lay down and die just yet. The AMA on the other hand missed the boat entirely with the drones. And then had to go and insult some 800,000 so called rogues. Another organization I wouldn't buy stock in.
My second question would be, define what you mean by "aeromodeling hobby". Does your definition encompass all aspects of model flight? RC flight? etc.