Catholics are not "worshiping" Mary and others in statue form in the same way they worship God - that is the difference. We pray to saints and angels and Mary and many others, and likenesses do appear in church and in other places, but it is not IN PLACE of God - I believe that is what is meant by the commandment. These likenesses are not "another" god -i.e. the golden calf - but an extension of the God that we worship.