At Preaching Today, Haddon Robinson describes the type of sermons we hear when our preaching is light on doctrine:
They end up being nothing more than moralisms: We should, we must, we ought. Or, here are three ways in which we can be better off financially. A sermon I heard a while ago on how to deal with procrastination had as its first point to get a Day Timer. You knew you were in trouble when you heard that. I have no doubt that when people left that church, if they were procrastinators, they thought it was a helpful sermon. But it was simply something that a motivational speaker could have done.
If people are raised on cotton candy, they are not going to grow as Christians. When Paul writes to his young associate Timothy, he says that 'all Scripture is inspired by God,' and that all Scripture is profitable for doctrine, for teaching, for putting the fundamental truths in front of people, and for 'reproof, for correction, for instruction in right living.' We have ignored that first affirmation – that the Bible is given to teach doctrine. It's not the only thing it does, but doctrine is first, and out of that there is reproof and then there is correction and then instruction in right living.