You do not disappoint him because you loathe running.
You confuse him. He was born not capable of understanding how anyone doesn't like to run.
You are confused by him. You think he wants you to run to become good. He wants you to run because it is the most fun thing he does every day. The reason he became good at it was that it was the most fun thing he did every day. Now, he fears that you will be unhealthy because you sit around all day.
You will be confused by your son if it turns out he hates to read. You will fear he will never get a decent job or he will live his life in ignorance. These cycles of confusion are all across the world and very old.
You need to talk to your father and tell him that running may not be your thing.
During that conversation you need to tell him that even though it is not your thing you will start running 2 miles every day. Tell him on odd numbered days you will run 2 miles easy and on even numbered days you will run 1 mile easy and the second mile you will alternate four 100 meter near sprints with 100 meter jogs and then jog home. Tell him you doubt you will ever run more but that you will run this cycle to stay in shape.
Ask him to read a book(s) you really like for 15 minutes every day so the two of you can discuss it during the mile or two you run slowly every day. Tell him if he doesn't do his reading and can't hold up his end of the book conversation, you will stop running just like he stopped reading.
Here comes the hard part. If the deal doesn't work the first, second or hundredth time, talk to him again and start it over at the beginning of a new month. This will keep the two of you talking. Talking is the only thing that will break the cycle of confusion.
A couple of hidden points. You need to think of this not as running every day but as talking with your dad about a book every day that you happen to do outside while moving. Second, while you may never become fast, at 14 to 18 years old, if you run 100 m near sprints every other day for several months, there is a pretty good chance you will eventually be able to beat your 40 something year old dad for the 4th 100m sprint of your run.