What makes you think civs that adopted Freedom cannot win via domination victory?
While freedom is mostly an economy idea, there are still some bonuses it can give you which can be very useful in war. Arsenal of democracy gives 25% bonus to unti production, and the vast amounts of happiness and wealth some of the bonuses can give can be very useful to warmongering player. The happiness makes the penalty from taking new cities less bad, and all of the money allows you to maintain a very large army.