In a culture that gave us the pet rock, marketing isn't the problem. The difficulty is in market domination. For most of human history religion was the only game in town, and a theocratic power structure was usually employed to make sure it stayed that way. Nowadays people can project their faith in any of a million different directions. There is really no difference between a revival meeting and the wave at a baseball game. Religion has, for all intents and purposes, become indistinguishable from any other brand loyalty. The most successful religions are little more than media empires for a reason.
Fiction isn't simple. Literature is one of the arts, and the arts are very complicated to produce and understand. Making art is like juggling spaghetti in a tornado. Everything you do retroactively affects everything else you have done and proactively everything you can do in the future. If science were like art-making the experiment would depend not only on the measurable qualities of the experiment itself but how the scientist feels about it, how anyone reviewing the results of the experiment feel and how all those feelings relate to the zeitgeist of feelings, expectations, fears, hopes and regrets of the culture at large over time and in relation to everything that has gone before. There has certainly been plenty of historical fiction since the bible was written and references to the world around the narrative are crucial to helping people understand what is going on and identify with the characters.
I doubt that reimagining Christianity again will prove helpful in the times ahead. Religion in general and Christianity in particular have hitched their cart to an expansionist mindset and here in the twenty first century with seven billion people on the planet and the specter of resource depletion, there is nowhere left to expand to. We may be on the cusp of another Axial Age, and any search for God shouldn't depend on the zeitgeist that got us into this mess.