Sometimes LOST fans ask, "Why a church in 'The End?'" In my view, by the time viewers reached the series finale, ideally they had come to recognize sacred spaces and their role in the story. The Island was important - but more as a classroom where viewers honed their recognition of the sacred, rather than as a final sacred destination in and of itself.
On-Island sacred spaces include:
the foot-statue rooms
the Heart of the Island
possibly the beach (because it's safe from Smokey)
the golf course
Off-Island sacred spaces include:
Christian's memorial service church
The Reyes's home ("The Lie," where Hurley tells his story literally under the eye of Mary)
The church where Kate gets married
The funeral home
St. Sebastian hospital
Santa Rosa hospital
the hospital where Locke recovers
Other off-Island places are the settings of powerful iconic moments, like the record store where Starla prophesizes about Hugo ("If you quit your job ... the whole damn thing will fall apart,") and the psychic's studio ("War is coming.")
Every one of these sacred spaces is like a passageway leading to another, and all of them together point to the church in "The End." All the sacred spaces we experience throughout the show build us up for the final one.
The church in "The End" is full of references to Divinity: not just Christian. Divinity is the terminus to which the entire story points. "Everything That Rises Must Converge" is the title of the book Jacob is reading because its writer, Flannery O'Connor, was giving a hat-tip to Fr. Teilhard de Chardin, who used the phrase to describe what he called "the omega point" - the convergence of humanity with the divine.
This "omega point" is what the Losties come to in the church of "The End."