Christians need to be able to explain (mostly to themselves, but if possible to others) why Jesus was necessary - what Jesus did that God the Father could Not do.
Traditional explanations for this have never satisfied me - they seem incoherent, inadequate or orthogonal to the problem. So here is my attempt:
Jesus is what enables us to know - and to know 'as gods'.
Without Jesus, God and Reality are incomprehensible.
Now, it is a fact that some people either do not want to know about God, or else regard the desire to be intrinsically blasphemous - and Christianity Is Not For Them.
Christianity is for those who want to know God, for themselves, by direct personal experience...
Why? Why would or should people want to know God? What is the point?
Because Christianity is about us becoming fully Sons of God - that is, on a parity (not equality, not sameness - but of the same 'kind') with Jesus Christ.
To become Sons of Gods we must grow-up towards becoming 'a god' (because a Son of God is a god - small 'g' indicating the distinction from God who is The Father and Creator); and as part of becoming a god we must know in the same way as a god knows.
(We can't just follow instincts, we can't just obey - we must know, for our-selves.)
Growing towards divinity is called theosis; but... not everybody wants theosis - and Christianity Is Not For Them.
What about our condition after death? In the first place, the Christian expects to be resurrected after death - to have an immortal body; but that is not an unique selling-point for Christianity.
For Christians there is more. When Jesus talked about Life Everlasting, he made clear that it was qualitatively better-than and different-from this earthly, mortal Life.
In the Fourth Gospel this difference is indicated in multiple comparisons relating to water, wine, bread, flesh/ body, blood and so on. For example, when Jesus explains to the Samaritan woman the difference between water from the well and the 'living water' he offers.
Thus, for Christians, after death they expect to be resurrected and for their state to be qualitatively greater than on earth; and to become gods.
Not everybody wants this - some people want oblivion after death (permanent sleep); others want a life just like this earthly life, but with more of the pleasurable and none of the miserable aspects (i.e. Paradise). Others want to become a spirit - freed from a body. Others want to remain as-children. Others want to rest forever, in bliss - others to be assimilated-into God (Nirvanah). And Christianity Is Not For Them.
The point I feel I need to take seriously is that Jesus was an incision in reality; Jesus changed 'history'; changed The Universe forever - All things, everywhere, and for every-body after Jesus, are different from how they were before Jesus. He was a transformation.
We first need to understand this, and second to decide whether or not to 'join'.
Because Christianity is an opt-in religion. Unless you have actively-chosen to opt-in, you are Not 'in'.
(Of course this 'choosing' is not a mere matter of conscious psychology, like choosing a cake from a shop! Choosing is an alignment at the deepest level of objective reality. And this is something we need to recognise - that there such a things as real, objective, permanent reality - regardless of our state of mind or knowledge-of-it - and this is the level at which Christianity is operating.)
