On talent alone, as a 15 years old, I was able to run a mile in 5:50 and a 5k in 29:00. With a lot of continuous training during 20 years, I am now able to run a mile in a little less than 5min and a 5k in 16:44. I also ran a marathon in 2h38 and a 10k in 33:54, just telling because both are being than my mile or 5k PR. But to get those results from my very low talent base, I had to log 50 000 miles in training, doing 3 hard session every week for nearly my entire life, running once up to 150mpw but most of the time between 50 and 100 mpw. Did gym work, yoga, all the stuff, and became along the road a certified mid-d and distance coach for more talented runners,.
So, training like a pro for a quarter of a century made me cut 1 min for the mile and 12-13 min for the 5k.
I am, I think, a middle of the range responder to training, i.e. that for each unit of training I do I get something out of it, but nothing magic here. Some very good responders get very good with very poor training or nearly nothing at all, while very bad responders don't get any better wathever training or amount of training they do.
Alex Vero, from Britain, did a good documentary on his experience from couch potatoe to living like a pro runner. The guy ran 1h13 for the half after 2 years of hard work.
But I would prefer talk about Nate Jenkins. This guy had a limited talent in High School and with a so good of a training ethic got himself to run a 2h14 marathon and a sub-14 5k.