If your attackers have Finishing, Long Shots and Composure around "10" then they won’t score and it doesn't matter what quality league you play... they won't score even if you play in the weakest league posible...
If a player has Finishing, Long Shots and Composure < "11" then it means you won't see goals from this player.
If a player has Finishing, Long Shots and Composure => "15" means this player score most of his chances.
If a player has Finishing, Long Shots and Composure = "20" means Messi or Ronaldo.