In all honesty, whether the accusation (that Christianity is more mythical than historical), if sustained, discredits Christian faith and the Christian church altogether may depend in part on how wide the gulf between Jesus and Paul is seen to be, but also on how important the historical Jesus is seen to be for faith. Many Jewish and Christian Scholars, along with ordinary Christians, would consider that the historical Jesus is by definition all-important for Christian faith. The vast majority of believing Christians today have not the slighest idea concerning the difference between "the Christ of faith" and "the Jesus of history."
If it turns out that Paul was not very interested in the historical Jesus, then traditional assumptions about the historical nature and basis of Christian faith are put in jeopardy. Christians traditionally have claimed that the distinctive thing about Christian faith is its historical basis: Its so-called 'particularity' lies in its assertion that God's salvation came to humanity in particular historical events - Christ '"as handed over to death for our trespasses and was raised for our justification" according again to Paul and "his gospel" (Rom 4:25). Christianity is not myth or philosophy or a system of ethics but a historical revelation. If, however, it turns out that Paul, as the first author of the NT and the most influential exponent of Christian faith in the early church, did not see the history of Jesus as especially important, then we will have to conclude that our view of Christian faith was not that of many of the earliest Christians, since Paul was surely not alone in his attitudes.
If Paul, perhaps influenced by the Greek mystery religions, was interested in the proclamation of a dying and rising Christ rather than in the history of Jesus, then we may be forced to conclude that early Christianity was more mythological and less historical than we supposed.
This is the sort of conclusion reached by a host of scholars in the last centuries. S. G. Wilson in his article surveying the history of recent Jesus-Paul study sums it up for us when he finds himself forced by the meager evidence for Paul's interest in Jesus to come to this theological conclusion:
Driven by reflection on both the theory and practice of our historical craft to the view that there is little we can confidently assert apart from the mere fact of Jesus' life and death, we are forced to fall back on a mythological figure (the Christ of faith, Pauline or otherwise) and adopt a position which verges on the docetic (Wilson, From Jesus to Paul)