I was doing "speed work" last Friday and thinking about this. All my PR's in running happened in the 80's and 90's. Now at nearly 60 my 400 repeats are slower than my average mile pace on an easy 5 mile run was 25 years ago.
We get old, we get injured, and life takes turns that we didn't expect, but at least we are still running, biking, and swimming, which puts us way ahead of the average person (at least in the US).
Are you in your 60+? Shouldn't be that much of a dropoff before that even for 25 year differential. I'm 25+ years from my 18 yr old self, and sure, while I never really 'maxxed' my run training in x-country HS, I'm faster now than I was back then, despite being 20 lbs heavier. I don't think I'll hit my age 30 maxxed PRs (done on up to 100mpw running) but it's not a matter of age there, it's a matter of lack of run-specific training.
And I think both you and I are on the cusp age wise of where things do start to drop off...
Fun times ahead!
I ran my first marathon not long after turning 19. I was still training at full mileage for an ultra 29 years later, having experienced few significant injuries over the years.
Shortly after that ultra in 2012, at 48 I realised I had run my ultra swansong. At least as far as approaching training and racing at a competitive attitude. Years of mileage inevitably took it's toll on my left knee> It was obvious that if I wanted to be active with running and hiking for years to come, it was time to scale back my training mileage, length of races, ambitions and distances on hard services.
After 50, circumstances and ability may change suddenly. Susceptibility to injuries, flexibility, overuse all have a potential to exacerbate the natural loss of speed attributable to simply being another year older.
Cherish you're speed while you have it. You don't when or how rapidly it may be compromised.
These days, I'm learning to accept that ParkRun will be at around my old 100km PR pace.