The situation you describe is not at all unusual, especially right now.
First, I agree with everyone here that it is simply not your son's place to voice his displeasure with his teammates' mistakes. Your son will make his own mistakes, no doubt, and this is a true "Golden Rule" situation. No matter what is happening on the field, he has a behavior lesson to learn here. You are the parent, and that makes it your responsibility to administer that lesson. If you do not, you can expect that eventually someone else will get their fill of your son and administer the lesson another way. That could mean a coach benches him, or it could mean that a teammate punches his lights out. Take your pick.
That being said, it has been my observation that while travel teams were once the realm of competitive players only, they are pretty much becoming the norm for even the weak players. Partly this is because recreational leagues have bailed on the whole notion of teaching the game in favor of having their coaches behave more like Barney the Purple Dinosaur, so that families are forced to look elsewhere to get even a rudimentary baseball experience. Partly it's because among the competitive boomer parents, there seems to be a mindset now that Little Johnny HAS to play travel ball to prove that he is as good as anybody out there. And partly it's because of the prevalent phenomenon of the player or dad who gets miffed and decides to show everyone by starting his own team, times a million.
The result of all this is that a lot of these travel teams are little more than glorified rec ball teams. And trying to make your current roster into a bunch of killers is a "silk purse out of sow's ear" situation.
There are always going to be teams who do collect only the best players and who play pedal to the metal baseball. It sounds like you need to find one of those teams, instead of the one you're on.
But be forewarned, if your son has developed a reputation for being a bad teammate, and if the parents have a reputation for being enablers of his bad behavior, when you find that team, they may not want you. So, first things first, clean up his act, and hope too much damage hasn't been done already.