I had this experience this weekend. I'm 48 (so I'll be pounding tables in frustration next year), and I was running a local 5K. Little did I know the local high school cross country team was using the race to test their summer training. Probably two dozen kids crowded the starting line at the start, and I actually thought of this thread.
Of course, they all took off at 800 pace, and most faded pathetically. I passed some of them after taking off at my even old man pace, and yes, I felt a little dumb working my way through a pack of kids, when I was probably older than most of their dads.
Afterwards, one of them came up to me and shook my hand and said he was impressed with my run. I think he was shocked that an old man could run like that. Yes, I felt dumb. I feel ya, OP.