Your team is a bit unbalanced. It had the sheer power to win the lesser cups, but the Striker Cup requires a balanced team with a definate winning technique.
What do you notice you have trouble with? What are you especially good at? You have three power shooters, one of which is a good passer. But Dry Bones is just in the wrong place, and your good passer is in the wrong place.
Not that it's bad to have Birdo and Hammers in the wings, but not with DK and Dry Bones on defense. You should try putting a good passer, like a playmaker, on defense to give you more control of your offense. Try losing Hammer Bro or Birdo for Dry Bones, putting him in the wings will give him good opportunities to score.
It might help us to know what it is they seem to be beating you at. And also keep in mind that the Striker Cup is tough.