You invert the order of the gospel

For, if you make your own faith, love, or good qualifications, to be your first and principle foundation, and you build Christ upon them, instead of building all upon Christ, you invert the order of the gospel, and Christ will profit you nothing. - Walter Marshall, The Gospel Mystery of Sanctification

Christ will not be an addendum, an additive, or an add-on! He is not the addition you attach to your already-formed foundation. He is the foundation on which you build everything else, or, He is nothing.

I think many North American 'Christians' approach Christianity in this fashion. They have a good job, with reasonable families, and passable relationships. They have things pretty much together. But this Jesus guy seems OK so they just tack Him on to what they are already doing.

In God's grace, some of these people realize that Christ is the center and starting point as opposed to a peripheral accessory. These people move from death to life. But many people never get beyond a shallow association with the matchless Son of God. And I doubt that sort of relationship will ultimately profit.