Is it really the churches' job to adapt to change?
Take for example the catholic church. It's among the oldest continuously operating organizations in human history. They can trace their history of operations all the way back to the apostles. Most of their history is chronicled in the same language the pope *tweets* in today, Latin (a language that has in its written form mostly has remained the same since the Romans spoke it). The church has stood by as empires rose and fell, they've been a persecuted minority, and they have been at the very apex of European power, they've seen not just medieval plague, but they remember the plagues that came before it, they've seen dynasties emerge and wither, they've seen bloody revolutions, economic booms and downturns; they've been around nearly two millennia and have seen more societal change than any of us can imagine, for the most part unflinching (although they did implement some extremely radical changes in the 1960s).
The greatest part about the church, for its many flaws, is just how resistant it has been to change, and we desperately need a connection to the past history to not completely lose ourselves in the whirlwind change of the present.
I'm not sure your underlying premise is correct, though. The 1960s weren't the only major doctrinal shifts in the church; just look at what things looked like pre- and post-Augustine. Instead, I think the Catholic Church remains strictly *because* it's been willing to adapt over the centuries.
Meanwhile, my reading on the statistics on religiosity and what-not is that people aren't actually becoming more atheistic, there are just fewer and fewer who feel at home in many denominations as they currently exist. Clearly there are needs here that are not being met.