Random numbers on a web page mean nothing.

If I look at my times on 200k brevets or perms, starting when I was 50 y/o to today at 61, it looks like:

Age Best 200k
50 8:55 (Living in Indiana, flat to rolling terrain)
51 9:33
52 10:05
53 8:25
54 8:34
55 8:40
Moved to flat west Texas
56 7:55 (actually this was in even-flatter Florida)
57 7:30
Moved to not-flat Oregon
58 8:30
59 10:55
60 9:03
61 8:51
62 9:00 (2 months into the year)

This data is not consistent with a dramatic loss in power from age 50 to 60. I'm no highly trained athlete; the only thing I've done is kept riding my bike and learned a few things about fueling and such.

I don't have any recorded data from before age 50, but I do recall riding the same flat rectangular 15 mile loop in my late 20's and early 30's. My fastest was 20.0 mph average. Fast forward to my first Strava ride in 2015 at age 55, 18 miles at 18.7 mph average on a non-flat route with stop signs and traffic lights through town.

Again not consistent in a dramatic loss in power from age 30 to 55.

I'm sure if I were trained to the limits of my capability, a significant power drop would be evident. But then if I were trained to the limits of my capabilities, all my numbers would be far better than they are, and certainly higher than those on the web page.