A religious leader once said "a religion that does not require the sacrifice of all things never has power sufficient to produce the faith necessary unto life and salvation."  Modern Christianity (painting with an awfully broad brush) has lost it's ability to require anything.  Many churches "come as you are"  "be yourself, God loves you as you are" "just be a good person" (without ever defining what "good" is).  In an effort to not offend, to be a "big tent," they've removed those things that actually require something--and that something is change of the person.  Christ's primary message was repent...turn to God.  Follow God's commandments.  The modern church has forgotten the <i>repent</i> part.  And, because there is little of value in the modern church, there  is little reason participate in it.

Notice that those churches that actually require something of their members actually are growing, not shrinking.  What does that teach us?