Forgive me if I am going on too much about The Exorcist, especially if it seems like my observations are trivial, but our conversation prompted me to re-watch parts of the film and I would like to mention one more thing that I noticed for the first time.I am wondering what was the main thing you took issue with in regards to the way the church is portrayed?
One of the points I am trying to make is that although some of the anti-Christian elements of the movie may appear subtle, they are part of both a larger Hollywood pattern, which I think most on this forum are aware of, but also part of specific patterns of film-making from the producer/writer Blatty, director Friedkin, and the lead actress Burstyn.
What I noticed was that when Father Karras first meets Father Marrin, the exorcist, they greet each other with a a Masonic grip of the third degree master Mason. Here's the screen grab from the director's cut version of the blu-ray.
Here is a figure from one of the most common Masonic references in North America (not that I'm an expert, just that I'm familiar enough to recognize some things), "Duncan's Masonic Ritual and Monitor":
Actors Miller and von Sydow do not reproduce the grip exactly the same way as shown in the manual, but it's very close and also quite distinctive from a normal handshake. Notice how Miller's index and middle finger rest on the middle of von Sydow's forearm near his wrist; it is totally different from a normal handshake and if anyone ever gripped you that way you would notice immediately.
Freemasonry is forbidden in the Catholic and Orthodox churches and to portray Catholic priests as Freemasons is another of the movie's blasphemies. I think one reason for doing this is that the producer/writer Blatty and the gay Jewish director Friedkin wish to be impious. Maybe I'm wrong to impute motives, but that is my conclusion after observing these patterns.
Blatty made a overtly Masonic movie in 1980, "The Ninth Configuration", which contained all sorts of references and allusions to their mythology and beliefs, so I think that like other Masonic directors*, he likes to insert symbols and references from his belief system into his films, especially when they can be used to show contempt for Christianity.
*A couple of films with extensive Masonic references:
The Man Who Would Be King (1975), directed by John Huston, starring Sean Connery and Michael Caine
The Three Burials of Melquiades Estrada (2005), directed by and starring Tommy Lee Jones