Again welcome to the website. Lots of answers and opinions within these electronic pages. All of my 3 sons played baseball through high school and one had the talent to play in college. Time goes very quickly. I get the impression your question is being asked through the lens of new baseball parent with a younger son. If your kids loves baseball as much as my kids did the best thing you can do is to constantly work with him to get better, AND make it fun. Kids learn quickly, and the better they get at baseball skills the more confident they get and the more they will enjoy playing and practicing baseball. Never stop playing catch, going to the batting cage, or crouching behind homeplate to work on pitching. This is a real special time, and an opportunity to bond with your son like no other. As I said earlier, it goes fast.
In terms of how to deal with coaches playing favorites...it happens. I've seen it, we've all seen it and a lot of us have experienced it. Step over it. Keep working with him on his skills. Sign up for different youth leagues and ask around about the best youth coaches. Word gets around about the best coaches. My kids were young playing summer rec ball and fall rec ball, and I always asked around about the best coaches. When good coaches weren't available, I volunteered to coach rec baseball. I got pretty good at it (I was told), and I eventually started a travel team who's goal was to get all our players to make their high school teams. When my kids got old enough they were trying out for various travel teams and playing rec baseball with their friends. As long as they were having fun, we supported them and worked with them on their baseball skills. By working with your son on his baseball skills you are controlling the things that you can control. As the kids get older, the Daddy- ball goes away and the Coach is under more pressure to win. When coaches are under pressure to win you'll see the 9 best players on the field which is based on their skill set.
Good luck!