Three kinds of law:
Divine law
Natural Law
Positive Law (i. e. man-made)
To my unprofessional mind, the problem seems to be this: suppose a pope changes something, or initiates something controversial (and just about everything popes have done for the past 50 years has been labelled controversial by some people).
Who determines whether the Topic was under Divine Law, Natural Law, or Positive Law?
Theologians often disagree themselves. You might argue, **we **can judge from Scripture or Tradition…but the **CURRENT **pope is always the ultimate interpreter of both of those. This means **he **determines what is Divine Law (unchangeable), what is Natural Law (unchangeable) and what is Positive Law (changeable).
In other words, you can’t use Pope Pius XII to refute Pope Francis. But a future pope, who is then the current pope, can identify some limits in the pastoral application of this or that past papal decree. But no future pope can change the Divine Law, or Natural Law.
The confusion is that some things relate to all 3 of the kinds of law. The topic of homosexuality might relate in some aspects to divine law, in other aspects to Natural Law, (both unchangeable) and in other aspects to Positive Law - pastoral practice, which may be changeable.
The alternative would be a nightmare. You could have one group of cardinals backed by CNN slamming the papacy one way, with another group of cardinals backed by Fox News pushing the other way; every month, every year. You migt say, this is a special time only during this special crisis…but the media would make every issue a crisis. This would greatly limit all future popes.