Well, I think that overstates the case somewhat, although there is no small truth there. And I think Warren and KLUV ("Positive and Encouraging") is in many ways to blame for boosting this trend along.
It's not so much that they ignore Christian theology, they emphasize and deemphasize it selectively. The unfun parts get deemphasized. The parts that make you feel good about yourself get emphasized. There is nothing in the Bible that says it's gonna be fun or that surrendering to the Lord will improve my self esteem or my inability to remember people's names or make me prosperous.
Ironically, a lot of evangelical churches don't do much evangelizing--unless by evangelizing you mean, "come to the big Halloween party, it'll be fun." OTOH, it is the first venture into Bible Study for a lot of folks. And once you start into that, the feel-good stuff ought to get harder and harder to swallow. It did for me. Now I'm Pentecostal.
One rule. If a pastor runs to the podium to music--I'm outta there.
But the bottom line on this is: A large part of the evangelical population are tweeners. They don't accept the degradation of secular humanism. But they can't get all the way to a Christian worldview. They want the good news but not the bad news. And as such, they are political 'tweeners also.