Maybe you shouldn't expect to beat these sorts of teams by that many goals. I do that and I end up being disappointed a lot of the time. The number of 1-0 results I got 2 seasons ago was crazy, especially in a piss easy league.
I find it harder to break down weaker teams than stronger teams. Sometimes their 3* defenders will play like 9* defenders and not let us through. When I play fully 5* teams my players will play their hearts out and score 3 or 4 and on other occasions against 3* teams we find it hard to score 2 goals