But why is Jesus Christ needed to achieve the blessings Osteen lists? If he took Christ out of his sermons could you still preach the same message? Probably.
Christ is needed to save us. He alone brought salvation into this world and offered it up freely on the Cross. He did this to atone for our sins. That is what people need to hear. That is the unpopular truth that Christians are called to tell others.
Nothing, nobody, no action, no belief, will ever, ever take the place of Jesus Christ when it comes to the fate of our souls. He is Lord. Preachers that gloss over that message are deceiving people.
The little I have seen of Olsteen, mostly interviews, I did not hear him preach the shed Blood of Jesus Christ. He may, but I have yet to hear it. As you note, we should not be focused on living in the world because His Kingdom is not this fallen world. We are to be as pilgrims for Christ in this unholy land.