If Jesus took all of our suffering and indeed died instead of us, why do we still suffer and die? Indeed, some of the most faithful followers of Christ have suffered cruel and terrible deaths.
If there is nothing more we can do for him, why does he tell us to "take up our cross daily and follow him"? Why are we told to "crucify the flesh with its passions and desires"? The way of salvation in Christ is much more than sitting passively on our spiritual tushes and singing hymns of praise. Salvation in Christ is the way of self denial, persecution, and trial. Show me where Jesus ever said, "I have done everything for you - all you have to do is to verbally accept what I have done."
What he actually said was: Matthew16:24 Then Jesus said to His disciples, "If anyone desires to come after Me, let him deny himself, and take up his cross, and follow Me.
Paul says: Galatians 5:24 And those who belong to Christ Jesus have crucified the flesh with its passions and desires.
Jesus wants us to enter to the same process of salvation that he did. We, like him, must crucify the flesh. If he did it all for us why should we have to do that? Jesus showed us the way. He lived perfectly. We can't. But he stands ready, in the love and mercy of his Father, to extend help and forgiveness so that when we fail, and fail we will, we can by his grace carry on toward his kingdom.
Would you even raise your own child the way you have characterized salvation? No you wouldn't. Why? Because you would raise a self-centred spoiled brat. God does not want spiritual "spoiled brats." He wants men and women who have come to spiritual maturity as His son did through trial and suffering and steadfast, faithful obedience.
We aren't "doing it for him" - he doesn't need our faithful obedience. We do it out of love and gratitude and for ourselves because we know that this life is a spiritual boot camp with tough training and preparation for the work that lies ahead in the Father's kingdom. It is not some posh "in-transit" lounge as many seem to think where all you need to do is sit in a cushy chair and sing happy-clappy songs until the rapture. It just doesn't work that way.
I hope you have found this helpful.