Kids' sports have reached a level of insanity, haven't they? My oldest is 17 and a high school senior, and my younger boys are 11 & 9 so I've seen my fair share of sports. And I remember feeling the same way you did when my oldest was that age. He actually didn't play anything at all in 3rd grade because he just wasn't interested in basketball, baseball or soccer, all which he had played for a couple of seasons before. In the spring of 4th grade, I asked him in passing if he wanted to try lacrosse and he was like "sure." I had no idea that the team had starting practicing in January (this was March) but they took him anyway and while he was definitely the worst one on the team, he liked it, and he played for 3 more seasons. At around the same time, he started pestering me about playing hockey (after declining skating lessons for years). I ignored his request and hoped it would go away because...hockey. Ugh. He kept at it and kept at it. So I borrowed some equipment and enrolled him in late-start lessons the summer before 5th grade, and he did several sessions of skating and skills in 5th grade, and joined a team in 6th, the middle school team, the JV team, and will play varsity this year. Tonight is his final game of rec-league hockey. I never would have believed you if you told me when he was 8 that we had 7 years of hockey ahead of us, and that the thought of his last game would make me want to cry, but here we are. Never a super star kid, never the fastest or the strongest or the biggest or most skilled, but always did his job on the ice and contributed to the team.
I know that looking at those other kids who seem to have sports sense - they get the game, the understand where to be and how to make plays, they are naturally athletic - it seems like they are the rule and not the exception. They're not. They really are the exception. Most 8 year olds really are a little clumsy and slow and uncoordinated, are fumbling around still learning their sport and learning their position. It's too bad that our crazy sports culture makes it seem like if a kid isn't talented and committed by age 8, he's washed up. That's insane, right? There are kids who excel at sports in high school and college that they didn't start playing until they were teenagers! And time and time again, the true experts say that playing lots of sports and not getting too involved in one is the best way to a) keep kids playing and b) develop healthy, athletic kids who aren't prone to overuse injuries or exercising only one set of skills.
So my advice? If he's happy playing, let him play. If or when he reaches a point where he feels like a team or sport isn't a good fit and wants to bow out, let him bow out. But he is on a team, he committed to the team, he is happy playing, so let him play this season and keep the long view in mind - it's about being active, working in the "stretch zone," learning teamwork and camaraderie, learning how to be coachable, and most importantly, having fun.