Why is it always the woman who is dominated?

The question is vague. If what is meant by "dominance" is the oppression and disparagement of women in some societies, then people's actions are not a proof but are weighed against the Sharia. No one's behavior can be an argument against Islam except that of the Messenger, peace and blessings of Allah be upon him.

If what is meant is the guardianship (qawamah) of men over women, then it is a guardianship of management and organization, not one of humiliation or dominance.

Freedom in Islam is restricted by the Sharia for both men and women equally, because absolute freedom means absolute corruption, and the true Sharia came to give every rightful person their due.