I always notice that there isn't much difference in the fastest times posted across the various age categories in sportive events. A lot less than you might expect. Some of the over 50s guys are still seriously fast and sometimes faster than the fastest of the over 30s and 40s. Maybe they have more time to train and less life stress? But there seems to be a very large decline in the over 70s.
From a personal perspective, aged 53, I've been consistently mediocre since my late teens. I can just about match my best benchmark climbing times today as I could in my early 20s. Which simply means I was under-performing back then. I eat better now and I train better and those things seem to balance out against my younger self - at least for now!
To put it in perspective I did a local timed sportive event yesterday and finished in the top 5 overall. That is not a major achievement as this was by no means a competitive event (fun ride sponsored by the local brewery) but it does show how you can be faster than pretty much anyone who doesn't train and ride regularly, regardless of their age. I was passing 20 year olds puffing along out of breath and most of the fitter looking guys were north of 40.
So I think lifestyle and genetics trump age up to a certain point, which thankfully I have yet to reach!