The teaching recognizes in the “signs of the times” that our time excels previous ages in a more civilized culture and refinement.
Morality does not change, however, there is always room for growth and advancement in our expression of it. As example, I choose the First Jerusalem Council’s prohibition against the consumption of blood (Acts 15:20):
abstain from food polluted by idols, from sexual immorality, from the meat of strangled animals and from blood.
Four centuries later St. Agustine wrote:
[T]he apostles did on that occasion require Christians to abstain from the blood of animals, and not to eat of things strangled, they seem to me to have [chosen an] easy observance … which the Gentiles might have in common with the Israelites, for the sake of the Cornerstone, … now that the Church has become so entirely Gentile that none who are outwardly Israelites are to be found in it, no Christian feels bound to abstain from thrushes or small birds because their blood has not been poured out, or from hares because they are killed by a stroke on the neck without shedding their blood. Any who still are afraid to touch these things are laughed at by the rest. - Contra Faustus XXXII
It should be obvious that the decree of the first Council, presided by the Apostles themselves, could in any way be ignored. But, since it was for a certain purpose and the necessity of that purpose no longer exists, it can be dispensed with.
It can be similarly argued that (in some parts of the world) the necessity of capital punishment no longer exists and can be dispensed with.