I think you're right about the "common good" point, except in the most general sense, since individuals' or families' "freedom of action" has to constrained by general laws against murder, theft, assault, etc.
Now, it is to the interest of the community, as well as of the individual, that peace and good order should be maintained; that all things should be carried on in accordance with God's laws and those of nature; that the discipline of family life should be observed and that religion should be obeyed; that a high standard of morality should prevail, both in public and private life; that justice should be held sacred and that no one should injure another with impunity; that the members of the commonwealth should grow up to man's estate strong and robust, and capable, if need be, of guarding and defending their country.
This indicates he takes the common good to be founded on peace and order rather than some elitist vision of "equality." And, of course, Pope Leo cites natural law in his defense of "the common good." The left has hijacked parts of this language to press their agenda, knowing that most of the unwashed masses will not take the time to critically examine the point.