Blame the midfield.
We used to sit deep and the midfield too slow to push up and too poor at passing to make the space on the wings.
It resulted in producing a winger that the only option was to head down and run at the full back, which was easy to defend against as it was so predictable.
Then when you did get a cross in the box the striker was either incapable of scoring or the midfield was way behind play to open the space.