I don't know the context but it sounds to me your coach doesn't seem interested in coaching you and doesn't want to encourage you.
Sounds to me that he wants you to quit. And doesn't want you to waste time devoting yourself to a fruitless endeavor and feel guilty about encouraging you wasting years in your life on running.
In the Pat Butcher book about Coe and Ovett I read the coach of Eamonn Coghlan even told him there was no way he could ever beat Coe.
So what. Very few runners have good genetics in this country. If you are banking your future on making the Olympics your coach is just breaking the news in a hard way.
If you can't break 52 for a 400 by age 20 you have no hope for ever making a US team in a distance race on the track. If you are a 28:30 10k runner by age 21 you might be able to run 2:10 for a marathon if you can handle the training and give it 4 years.
I've seen numerous guys that lacked talent to move into elite levels stick with it and improve after college to 2:15-2:20 marathons.
Eventually you will have to decide when its time to stop focusing the majority of your life going for running goals. It takes up a major life focus. I wouldn't tell anyone how to live their life but as a guy who has been there I would have put 25 years old as the limit.