First, take EVERY piece of advice on here with a grain of salt. You and I are cut from the same cloth, and most people do not understand extremely motivated individuals who have low trainability and aren't especially durable. Lots of people on these boards just don't understand that some bodies do not simply absorb training readily and let you cut your 5k down to a 16:00.
You are a low-trainability runner. So am I. Read the Sports Gene by David Epstein, but here is a quick primer. Studies have shown that some people show immense training gains with aerobic training, others show almost none, and most people are in the middle. It's genetic. You are probably in the middle-low end of the spectrum.
I am now 29, so I have some perspective. It WAS frustrating to get leapfrogged by younger runners doing less training. It IS frustrating to love running some much and still be unable to improve how I'd like. You are young enough there is a small hope-- a testosterone burst from the later stages of puberty. Mine never happened... I looked the same physically as a senior as I had as a freshman.
My PR's were 4:56, 10:42, and 17:47, so you and I were pretty similar. I still run, and am glad I stuck with it. You have to learn to be happy with incremental improvements and treat them like the victories they are. I was fortunate that I went to a smaller school and was still able to crack varsity and be a scoring member of a state-qualifying team, so that gave purpose to what I was doing.
Lastly, consider that you might be running too hard too often. Read Wejo's "Why I sucked in college" for how that might be the case.
Good luck. It can be frustrating, but compared to the great genetic sea out there, you still ended pretty fortunate if you are cracking 5 in the 1600. Focus on those incremental improvements and try to tune everything else out.