Oh my, this resonates but in very wrong ways. I spent much of college focusing on the connections between mythology, ritual, archetype and performance. While I find their argument that theatre could substitute for religion to be intriguing, I think their approach in the article is too simplistic. (Warning: I have a liberal arts degree and I occasionally whip it out.)
For one, while they did briefly mention the Greeks, they totally missed the most obvious historical and non-western connections between theatre and religion. After all, theatre as we know it evolved directly from religious practices. There is a direct evolutionary path from shamanistic ritual to classical Greek theatre. They don't touch on mystery plays and the medieval morality plays. They don't address the mask and puppetry traditions in areas such as Bali and the Pacific Northwest that are simultaneously performative and spiritual. They completely gloss over the evolution of dance and the importance of it in multiple religious traditions. (Of course, dance - I'm thinking particularly of capoeira here but there are others - also evolved from non-religious sources but so did theatre.) Personally I would even argue that modern civil war reenactment is not so far off from ancestor worship.
I think that any situation where a large group of people behold a single source of information is bound by a common thread to all of its sibling events, but that does not mean that any one can substitute for the other effectively. The three factors that strike me as variable are the malleability of the information, the location of the audience and the level of interactivity (for you semioticians out there, that is, the treatment of the liminal space/fourth wall).
Live theatre reinterprets its information differently at every iteration. Much of theatre, excluding improv, demands a silent audience in a single location. It is rarely participatory. Live sporting events and concerts provide a similar randomness of the information, as does "reality" TV, although the former requires a united audience in a single location while the latter disperses the audience globally. Movies and television provide a solitary and unyielding interpretation with absolutely no unity of space for the audience - yet I would argue that the event continues long after the transfer of information has ended, through discussion about it between viewers from different locales.
Western religious ritual relies heavily on the perpetual reiteration of the same material. It demands interaction but with varying levels of fourth-wall puncture. At the High Catholic level there is connection between the congregation and the priest only at communion, but if you go beyond that into the gospel traditions or the more vigorous protestant religions the services are more of an improvised dialogue. The perverse beast known as televangelism demonstrates that western religion does not mandate a common location. I have not attended services for any of the other "big five" religions - I've attended a seder and have heard tell of a Hindu wedding but I don't know enough about any of them to say if they uphold my thoughts here or skewer them utterly.
However, I think that each of these forms of ritual/performance could be considered necessary to a thriving culture. But you will not necessarily see a Nascar fan enjoying the opera and you won't necessarily see an improv fan enjoying a baptism. The consistent popularity of all of these types of spectator rituals indicates that each combination of information, location and interaction sates a different need. Some might be able to conflate them and achieve satisfaction through substitution, and some might find their particular itch is better-scratched by theatre than religion, but in a blind taste test 9 out of 10 people will be able to pick out one from the other.
