But it hasn't changed on this issue and it's very unlikely Pope Francis will make such a change. Why? Because some Canon Laws actually reflects established doctrine and cannot change because discipline and doctrine are indistinguishable. 

If one believes in a Creator who has purpose in His creation, and who made us in His image and gave us a moral compass to live as we ought for our own good and that of others, then of course their is "objective sin". What would the wanton murder of a child be if not objective sin? 

The idea that sin is a "human construct" stems from a view that natural selection blindly created us and our behavioural imperfections stem from our struggles to socialise and civilise our brains that were biologically shaped in prehistoric eras.