I consider myself a respectable runner, but definitely not fast.
I started running on my own about 20 years ago (at 18). Never ran on a team, just gradually improved to the point where I could occasionally win local, low key races. It was around then that I did actually consider myself fast.
Around 10 years ago, I started taking training fairly seriously. Started running with a group, started running more competitive races. This is when I really learned how much better other runners were. Exposure to this level of running has helped me to improve as a runner, but I haven't considered myself fast since then (and honestly I'm 100 percent ok with that because I love training, running and racing even if I'll never be elite)..
There have been a couple times where people have introduced me as a fast runner and it makes me feel really uncomfortable.