No doubt about it... Coaching matters at every level. However, there are definite priorities that might change depending on the level.
First and by far the most important priority at the younger ages is to make sure the kids are having fun at the same time they are learning some of the basic fundamentals. As they grow older that really doesn't change, but the everything gets more advanced.
There are good and bad coaches at every level and yes they make a big difference in a players experience and development. And winning at the highest levels. They are just like the players, some are much better than others.
Personally, one of the most important things that sometimes gets overlooked is teaching players how to act. To respect the game and to show some class. It's also important IMO that your players are comfortable. At every level there is pressure that the game itself creates for those that play. I have never understood why a coach would want to add additional pressure by downgrading, yelling, or embarrassing one of his players in front of everyone. To me those things just add more pressure and add discomfort. You want your players to play relaxed (not to be confused with lazy), loose is better than tight. They need to be comfortable, focused and intense all at the same time... Yes that is possible.
Every coach should put together a playbook of sorts. At the very youngest ages it can be very simple. Things like be nice to your teammates. Always let the coaches know if you're not having fun. Stuff like that! then as players grow older the playbook would be far more advanced. You will want team rules included. In college we had a playbook that was over 100 pages. When someone would make a mistake during a game a note would be made and we just continued playing. After each game we would get together and go over any mistakes in a fairly calm atmosphere. Seldom would a player make that same mistake again and as we talked about it, the entire team was learning not to make that mistake.
At the more advanced levels where winning is most important, there are many different type coaches. They go about winning in different ways. Things are very competitive and different styles have been successful. The thing we always preached to our players was that there are four things that determine success or winning a game. They are the only four things we need to deal with.
1. TALENT is the most important. Understand that talent can be developed and improved, but you have to have it. Sometimes we will have more talent than our opponents, Sometimes they will have more talent.
2. EFFORT. Never will we ever play a game when the other team beats us in effort.
3. INTELLIGENCE. Never will we play a game where we are the team that is less intelligent and prepared.
4. LUCK. Sometimes luck will determine the outcome of a game. But if we are better in the other things we are more likely to experience the most luck.
So every game we knew that we were ahead in at least two of those ingredients. Sometimes those two were enough to win games against teams with better talent. If we were the best at the first three the only way we could lose is by bad luck. No matter what, the team would always be very confident because we knew we were the better team when it came to 2 and 3. Over time that effort and intelligence also helped create more talent, also.
If you stop and think about it, those four ingredients can be the determining factor in having success in many things beside baseball. I once asked our players if they knew of any other way to win a game. One of our players said, how about cheating. I thought about that and asked, what do you consider cheating? Is it cheating if we are stalling to buy time for our relief pitcher to get ready. Anyway this led to a long discussion about cheating.
The topic of fake tags came up. Is it ever OK to throw down a fake tag? Truth is, it is not only OK, it is good smart baseball depending on the situation and play. If my fake tag or other type decoy keeps a runner from advancing it is a good play. Now if the fake tag or decoy is used for no real purpose other than to possibly get a runner injured by sliding late, that is altogether different. That is a cheap low class move that has no place in baseball.
I once had a player that went to the AD complaining that I was teaching the team how to cheat. So I must have confused him along the way. The AD and I talked about this and ended up laughing about the whole thing after I gave him examples of cheating. I think by using the word cheating instead of something else, the player thought we were against good sportsmanship. We got it all figured out, I was kind of disappointed that one of the players went to the AD rather than talking to me. I'm sure it really had more to do with his lack of playing time, than anything else. His playing time did not increase.
I'm sorry that sometimes I get long winded when posting. It's just that one thing reminds me of something else.