It used to be that 'mainline' was an accurate term for those within the category. This term is for more established and historical Protestant denominations: Methodist, Presbyterian, United Church of Christ, Christian Church (Disciples of Christ), Lutheran, and so on. I find myself beginning to use 'oldline' a little more, and if someone can conjur a more endearing term I'd love to start using it instead. As 'non-denominational' churches are on the rise, 'mainline' is not as fitting a term any more.
The explanations for this decline are numerous and in some sense reflect one's own biases (some good, some bad). Let's just get a few theories out in the open.
~Why Men Hate Going to Church has its own explanation: the men aren't there and culturally speaking they're still the ones that other men will follow. One man sees another man going to church, they might be more inclined to come. There's an element of sexism and insecurity that underscores this explanation, but the author repeatedly states that 'this book is about how men actually are, not how they should be.' Furthermore, the author states that if the husband/father is in church, the rest of the family is more likely to attend as well. MUCH more likely, in fact.
~An explanation that has quickly become a classic among 'conservatives' is that the 'liberal' theology many 'mainline' churches profess, with its non-answers and 'anything goes' philosophy (a gross mischaracterization) turns people off, or toward churches with clearer answers and more rigid doctrine. An explanation close to this is that many 'mainline' denominations have been overtaken with those wishing to push a 'liberal' political agenda. Because we know that if 'conservatives' were in power in these churches, a political agenda would never be pushed *coughSBCcough*. Nevertheless, theological and political divides have taken their toll.
~Supporters of said 'agendas' have a much different take on the above. They're being faithful to the true gospel that Jesus preached, that is, care for the least of these. They're being prophetic, and of course that's going to upset people and compel them to leave. There's actually a certain level of rejoicing that takes place when people get mad and transfer their membership or when a church pulls out. Some see such actions as a sign that they're doing something right. Those within the UCC at least who don't agree with the stances of our national office state that such a view violates our polity as we strive to be a 'united and uniting church.' A congregational tradition that makes pronouncements from its national setting? Those citing polity cry foul.
~One of my favorites, John Cobb, writes that 'mainliners' have been suffering from a lack of theological passion. People aren't excited about what they're doing. Christian Century offers a similar commentary this week. 'Mainline' churches have been so used to being 'mainline' that they just roll with what they've been doing, not always realizing when it doesn't work any more. A 45-minute Sunday School lesson is enough to enrich people's souls every week. It's all people have time for anyway. The passion is lacking in part because people have put other things in higher priority on their schedules and in part because 'mainliners' haven't offered anything different, at least not lately. A parishioner of mine recently spoke to me fondly about the days of Wednesday night prayer meetings. I remember that it wasn't that long ago that the local banks and library closed at noon on Wednesdays so people could prepare for church activities. But with other things cluttering schedules, that's become a thing of the past in many 'mainline' churches. This point got away from me a little bit. Ah well.
~Worship is boring. Three dirges and a 20-minute lecture is not attractive to many. The other extreme of course is theologically lite choruses and a 40-minute pep talk. I've talked about this before and given my answer to it, so that's all I'm going to say about it right now.
I could continue with these, but I thought this would be enough to get us started. I haven't always been good about multi-part entries here, but this is something in which I've taken an interest recently because I need to. All of us 'mainliners' need to.
Part 2: A more extensive review of Why Men Hate Going to Church, which will touch on other points listed here.
Part 3: My own take on important elements to a vibrant and relevant church.
Part 4: Final thoughts before General Synod.
Obviously this won't be an exhaustive look at the situation. But the comments section is available for further discussion.