Chances are your PRs aren't very good any way, so why were you ever motivated to run? I'd bet that compared to the elites you are terrible.
But I guess you received some degree of satisfaction from setting a goal and reaching, you liked the workouts, the routine of doing something physical every day, and you enjoyed the health benefits along the way too.
Training for PRs and FKTs are fun, but that fun eventually ends for all of us. I’d say try longer events and building the slow twitch fibers. Honestly is shaving off a couple seconds going to make you that much happier? If running doesn’t make you happier mentally and spiritually then I’d quit. Always examine why you do what you do in life. Stop just going through the motions.
No point in training anymore just run for fun and health
on one level, try another event or sport like they are saying. if you do distance try a hurdle or sprint or field. or maybe try soccer or some sport where you run and endurance is valued but it's not a race per se. it's no longer i won't be as good as before, it's how good can i do this new thing. the challenge of learning it and progressing for a while.
on another level, this is just reality for everything and you need to come to terms. i tried another sport. i got physically beat up to do it too and started falling back off. it is just what's going to happen. i would look at where am i just fine and where am i beat up and shift to what is easier on your current body.
to me this would also be a good time to figure out what outdoorsy or sportsy stuff you just enjoy for its own sake. to me this is one thing this country stinks at that someplace like norway gets. figure out if you love it first. at this point it starts becoming what would i like to be doing on a wednesday night or saturday morning.
personally when i hit the point you did i just started trying new things. not "a" thing. like, this week i am going to take classes at kayaking. or sailing. or a list. for a couple years. and then a couple things stuck.