I was delighted to see another series directed by Mike Flanagan as I absolutely adore the Haunting of Hill House.
Midnight Mass starts very slowly taking great care to introduce the characters, their challenges, and establish what life on Crockett Island is like, which proves to be very important by the time you reach the end as to trigger sympathy for the characters and a deep understanding of the setting from the viewers. This is an excellent scriptwriting technique for those who are intrigued enough by the little hints of supernatural mysteries to keep on watching. Those who don't quit before the plot is revealed won't be disappointed.
It is a Christian Redemption Story turning to supernatural horror with the central themes of Addiction, Moral Compass, overcoming prejudice, the meaning of Death, and its universal fear.
In the end, one can deduct that things aren't always what they seem and people who have done terrible things aren't necessarily inherently evil, just as people who tend to regard themselves as holy aren't inherently good. Midnight Mass paints a canvas of humanity's intricate existential crisis.
"Beware of false prophets, which come to you in sheep's: clothing, but inwardly they are ravening wolves." Matthew 7:15