The cabins that do connect have heavy doors on "both" sides. So if anything, the sounds, if any, will come from elsewhere. IMO.
IOW, not from the connecting double heavy doors. The sounds will come from the walls or halls.
You can also place towels at the gap in the bottom of the door to help muffle the noise. On any doors.
In fact, open the connecting door. Carefully stuff proper sized towel in bottom gap, (bath mat has always seemed the right size for us) close your side connecting door, add additional towel on your side door bottom connecting door.
Sound should be solved. At least sourced from connecting door.
We do this all the time. Jamb towels at the bottom of doors. We do this all the time in Hotels.
We will admit never needed on the Fantasy, but ... upper most forward decks have less noise naturally.
So, do this at your cabin entrance door too obviously. Once inside for the night obviously, To limit hall noise.
Just sharing our tactics.
HTH