I would guess that there are almost as many people enjoying building today as compared to 20 or 30 years ago. The difference is that 20 or 30 years ago, if you wanted to fly, you needed to build.
ARFs have done two things. First, those that don't enjoy building, don't have to. Second, there are many who, by not being forced to build, have not descovered the pleasures of building.
For myself, I enjoy building more than flying. I just finished my first sport scale plane and getting ready for my second. I have about 7 kits waiting, mostly Royal/Marutaka kits.

Scott