I agree about the historical Jesus studies. At one point, I got intensely interested in this topic and read a dozen or so books about it by various authors (mostly on the skeptical end). My conclusion is that this is possibly the ultimate example of an area where the questions are tantalizingly interesting, but making any reliable conclusions from the available evidence is basically impossible. At the end, as you say, we get a lot of well written and impressively researched books whose content is however just a rationalization for the authors' opinions held for altogether different reasons.

On the other hand, I'm not sure if you're expressing support for the radical mythicist position, but if you do, I disagree. As much as Christian apologists tend to stretch the evidence in their favor, it seems to me like radical mythicists are biased in the other direction. (It's telling that the doyen of contemporary mythicism, G.A. Wells, who certainly has no inclination towards Christian apologetics, has moderated his position significantly in recent years.)