That is, why do people not recognise Jesus for who he is? If he really is who he claims to be then surely that should be apparent? He should strike an echo in every human heart. But even during his lifetime there were plenty of people who saw and heard him but did not recognise him and so consequently rejected him. And now, though you might think he is plainly revealed in scripture, religion, tradition and art, there are many who do not recognise him.
I would say there are several answers to this but they each have to do with the failure of a particular human faculty: something that should be open, and would be in an unfallen world, is closed, either fully or partially.
These faculties are the intellect, the imagination and the will. If properly functioning, each one of these should be able to recognise Christ. If correctly orientated to the good, they would all see the truth of Christ and the person would respond accordingly. So, the fact that one does not recognise Jesus points to a defect in the individual concerned.
For those who have grown up in a non-Christian culture the situation is a little different. We are all influenced by our environment, and what has developed in an alien environment may not sit comfortably with us for various reasons to do with habit, custom, loyalty and sense of tradition. But most people in Europe and America are the product of a Christian culture, even if that is now at one or two removes, so they do not have this excuse. And actually, even those who have been born into one of the other world religions might be able to see that Christ really is something more than anything in those religions. They all have aspects of him but not him revealed and in his fullness.
Let us take these human faculties that should be able to see Christ for who he is one by one. First, the intellect. I am using this word not only in the sense of reason (as opposed to faith) but also that in us which enables us to know and to understand. A more highly developed intellect should certainly be able to understand more of Christ but I believe that a properly functioning intellect at any level should be able to see the truth of Christ. If our mind is open to truth then we should know Christ. I am not disputing that, to such a mind, doubt and uncertainty might also be present, but these are only primary when the intellect has become clouded by worldliness.
The imagination is that in us which opens up the mind to what is beyond sensory perception. A correctly ordered imagination, one uncorrupted by egotism, demonic influence or unholy desire, would respond to the reality of Jesus. It would see the truth in a passage of scripture or a story from his life or even a great painting. It would see the truth in him and him as the truth. There would be something like an inner opening such as when the bud of a flower is touched by the sun.
When the will is directed to righteousness and truth then it can respond to Christ but if it is centred on itself and its own ends it may well fail to respond as it should. So, if we do not recognise Christ it could be because we do not want to, either because we do not want to behave in the way that would require or because we do not want what Christ promises.
I recognise that there are mitigating circumstances in all these cases, particularly for people living nowadays. Many people are not properly introduced to Christ. Either they do not meet him at all, knowing of him only at a distance, or else they are given a false image of him, one distorted by human beings, and they reject that as inadequate. But even these people have a responsibility to seek out the truth and not just be satisfied with secondhand knowledge. Somewhere inside us all we know that we have come to Earth for a spiritual reason and we should therefore seek a spiritual answer to the question posed by our existence in this world. If we don't, that is our failure, tough as it may be to accept that statement.
Many people now in the West who do seek a spiritual answer look elsewhere than Christ. This is partly because the churches have not been able to keep pace with the evolution in human consciousness, particularly over the last three centuries, either mistakenly adapting to secularisation, in which case they are perceived as beside the point, or else failing to respond to increased intellectual development and the need of modern men and women to know and not just believe. They have not emphasised the inner path of theosis as they should have done which leaves the field open to Eastern mysticism and a host of other esoteric practises. The fact that the grass is often perceived as greener on the other side of the fence while the familiar becomes stale also contributes to this.
However, spiritual approaches which do not have Christ at their centre risk becoming focused on the human self. This may not matter so much at an early stage of the path but becomes very important later on for Christ is the true image of God and the only direct signpost to him. He is the gateway through which we all must pass to eternal life and we can only do this if he is stamped on our heart, showing that we have emptied ourselves of self and accepted him as the true form of God. Now, other religions may have pointers to Christ because he is present in them in their most spiritualised forms, but he is only fully present as himself and if we would become sons and daughters of God we need to recognise him as the true pattern and template. Only when we recognise Christ can we really rise above ourselves.