This is what I recall:
Circa 1949 to 1966: 17 years, the early days: Just one class, 4 pounds and 44" wingspan, scale only, all the power you could get. This worked fine until newer high-powered 65's made the event too fast, powerful and dangerous for most people.
1967 to 1975: 7 years, The Golden Age. Profile and Class I were added, bringing the event back into the grasp of many more modelers. Profile was designated as an "entry" class and separated from the scale classes at The Nats.
1976 to 2023: 47 years, the decline and impending demise of Carrier. The rules change that massively increased low speed scoring and made sliders effectively mandatory got rid of the majority of active flyers without bringing in anybody new.
2024 onward: We have two rules proposals under review. They are certainly NOT what I would have proposed. They will effectively obsolete the equipment of about three or four people who currently dominate the event. But, hey what's new? The rules change of 1976 wiped-out maybe 100 competitors. 47 years!! They got money's worth.
I fly all the categories. There have always been rules changes in combat, racing, stunt, speed, and scale that render equipment either obsolete or illegal. Even without rules changes, new equipment replaces the old. Sometimes old time or nostalgia events bring back the old stuff.
If the two proposals pass I will make planes with fixed leadouts and maximum wing area and just fly slow at a 28 degree angle like a real airplane.
There is a chance that the elimination of the hassles of sliders and five-minute low speed will bring in more than the two people who might quit.