For years people have been touting a line about losing react time when you hit 23-24 years old, no idea if it's apocryphal or not I haven't personally seen a study or whatever.
I lost interest in competitive / PvP games well before then, they could be right and I wouldn't know. It isn't a noticeable issue if you only play map pervert games.
I have 100% gotten worse at video games after 25. I don't think it's reflexes, I doubt my reflexes have changed enough to matter for the gaming I do. I know at least part of it is lifestyle. I can't put as many hours into gaming anymore, I'm out of school and tbh I'm a bit out of the habit of pushing myself mentally, which I think has made me a slower learner. Actually I'm glad I'm typing this out cause I hadn't thought about it this and I'm sure now that I'm aware of it I can turn the trend around.
Clicking mouse requires 82% more brain power than your average “musician.” Beethoven can write a symphony but he can’t hear footsteps coming up to knife him 🥱