There is a Catch 321 Situation involved in the question of the authority of Apostolic Exhortations. It arises from the fact that no Apostolic Exhortation has any more (or any less) 'authority' than any other Apostolic Exhortation. This 'Catch' can be invoked to embarrass both 'sides'. Thus: -
Trendies can be told "Your enthusiasm for Amoris Laetitia is undercut by the fact that it has no more authority than Familiaris consortio".
Traddies can be told "Your enthusiasm for Familiaris consortio is undercut by the fact that it is cancelled out by Amoris laetitia".
Both of these documents are Apostolic Exhortations.
And Apostolic Exhortations are neither doctrinally constitutive nor canonically legislative.
The principle that public adulterers, even when repackaged as "remarried divorcees", ought not to receive Holy Communion, does not rest upon the authority of Familiaris consortio or Sacramentum caritatis. It is a principle based upon some of the most explicit words that the Incarnate Torah is known to have uttered, combined with a very blunt statement by S Paul, who was even more Apostolic than the authors of Apostolic Exhortations. It is a principle to which the daily praxis of the bimillennial Church, and many of its official documents, bear witness.
Familiaris consortio and Sacramentum caritatis did not constitute, set up, create, the principle concerned. They (very laudably and eloquently) bore witness to it.
In Apostolic Exhortations the Roman Pontiff exhorts the Faithful to abide by what is already the authentic teaching and praxis of the Church.