It's a fairly normal problem when you start running. I definitely found that I had to slow my pace down significantly from what I naturally wanted to run at before I could make 5k/10k distances.
Don't worry, that is exactly the words you must use when talking to other runners, who will understand this is about long-distance and everyone know that running too fast is a problem.
For the HNers not used to running, every long-distance running is more a matter of strategy than speed. Even in the Olympics. Go watch a 5,000 meters of any Olympic Finals and try to analyze why the losers sometimes could have easily ran faster than the time of the winner (according to their historic results) and still they didn't.
I think it only sounds arrogant to someone who doesn't run, or who has never experienced the problem.
I started running in March of this year, after having lived 35 years of my life believing that there was something wrong with me that physically prohibited me from running. Every time I tried running, I would end up gassed very quickly, with my heart rate shooting up to 180 bpm. I tried all sorts of things, but it turned out, I just ran too fast. Surprisingly, this isn't something anyone thinks to tell beginning runners: slow down. I found that I had to focus on running slower than was comfortable in order to get my endurance up. It required real, conscious effort to slow down.
I don't know how many people experience this problem, but I know it was a giant hurdle for me. Your app seems like a really fantastic idea.
I think that's something that most beginner runners don't think of. Endurance base is so important but also the one that is neglected a lot of the time.
It's easy to think "I want to run fast so I have to train fast" but it's harder to get into a mindset of "I want to run fast so I better not tire out as quickly". Long steady runs are the best way to build this up (long being relative to your level, of course)