no it has nothing to do with you not attaching the feet to the character.
If i'm not mistaken you should increase the resolution of your cloth object .
Select your character and set collision ofset and debt to 0.3/0.4 .
then turn the solver scale a bit higher to 4 or 5.
i'm not sure if this will work for you, since i don't know the size of your model and what you previously have tried, but ussually this will work.
good luck