IMHO, there if parents/spectators understood a few basics, they would enjoy and understand the game much more:
1) The Laws of the Game require the referee to actually "see" the foul to call the foul. If the referee's vision is blocked or their attention drawn to another area of play, that elbow 20 yards away from the ball and behind the referee will go completely unnoticed by all except the victims parents who's focus is always on their kid. The referee is only permitted to rely on the ARs. Parents and Coaches and Players are excluded from the "review committee."
2) A foul is "careless," "reckless," or "excessive force" play. The corollary is that every player owes a duty of "care" to their opponents. This means that a player can actually get to the ball first, but if that player did so in a careless manner, its a foul. Shouting "she got to the ball first!!!" is evidence of a parent that is uneducated.
3) The Laws of the Game encourage a referee to not call fouls if "trifling" in order to not disrupt the flow of the game. In other words, yes it was careless, but had no impact on the game/play, therefore, we don't call them. What is a trifling foul really depends on a number of factors, but the temperature of the game and skill level of the athletes all play into that consideration. Most of the excitement I hear from the peanut gallery is parents losing their minds at a Referee who isn't calling trifling fouls.
4) The Laws of the Game allow a referee to not call a foul if the fouled team retains possession ... this is called "advantage." A similar concept exists in football, in that a referee throws a flag and allows play to continue, after play is stopped a team can "decline" the penalty. With reckless or excessive force plays, the referee is also empowered to "caution" or "send off" the player minutes after the foul once play stops.
5) "Handling" aka "handball" requires the referee to determine the player "deliberately" acted in a manner to handle the ball. Just because a ball kicked from 10 yards away hits the opponent in the hand does not mean its handling. We look at time to react, skill level, whether the hand was in a natural position, was the player deliberately making themselves bigger, etc.
6) Referees are human and make mistakes. The Laws state "Decisions will be made to the best of the referee`s ability according to the Laws of the Game and the ‘spirit of the game’ and will be based on the opinion of the referee who has the discretion to take appropriate action within the framework of the Laws of the Game. The decisions of the referee regarding facts connected with play, including whether or not a goal is scored and the result of the match, are final. The decisions of the referee, and all other match officials, must always be respected." The Laws of the Game recognize that the referee is operating with imperfect factual data which forms the Referees opinion. Whatever that decision is/was, is final once play restarts. Soccer is designed to be an imperfect game, its part of the Laws.