The difference in chance creation is mainly due to formation counters. But if you constantly getting low number no matter what team you are against, your captain may be the cultprit.

The role of the captain is linked to your overall strategy. If you are playing defensive mentality, avoid using STs as captain.
If you have AM or ST as captain you should be playing attacking mentality.
Likewise, hard defending work best with D or GK as captain.

Aging player who have been in your team for a long time make the best captain, but more importantly is the player form as a captain with bad form can ruin the entire team.