Remeber that it is all relative. Also remember the player ratings arent exactly precise.
If you trash a team 10-0, al your players will have an 8/9/10, even your goalie who hasnt had a save to make. Point being, is that if you play very attacking and score lots of goals, ratings will automatically be higher troughout the team.
Playing more cautios and winning 2-0 everything is just as succesfull, but the avg. rating will be much lower. You've still done as well though.
The way you should look at it, is judge how succesfull you are and look at the average average rating through your team. If the average avg. rating is 7.20, then this is very good if you are winning everything.