There have been a lot of discussions on this over the years. There is no real consensus but generally it seems like someone untalented could probably get around 15/31 by going all in on training and lifestyle through hs, college, and post collegiately. Yes, that wouldn't even be fast enough to walk on a lot of teams. For this to be worthwhile, an individual would have to be motivated by personal improvement, not placings.
But this individual can probably walk on some d2, naia, and d3 teams. Chances are they pursued running either because its fun or they suck at the ball sports. In the latter category, they won't even be good enough to walk on d3 soccer, football, etc. Up to you whether you want to be a college athlete or just a guy who goes to the gym most days and runs the turkey trot.
These individual usually get better as the distance goes up. They can probably get down to low 2:20s in the marathon and around 107 in the half. Those times might make this individual the top runner in their club.
Here is another brutal truth: Due to our modern lifestyle, people have to exercise to stay healthy. Might as well channel that exercise into distance running if you find it fun or aren't talented at anything else.
The sooner you check the ego - and stifle the need to be the absolute best, the sooner you can focus on personal improvement. Pr'ing and beating yourself (plus as many people as you can). is fun. Being sad because you can't run a 3:55 mile and walk on at Oregon is not.