Religious principles are true
 

but interpretation of historical and scientific processes are not necessarily correct, as the interpreters frequently lack all the principles necessary to construe them in totality.

That's the difficulty of being an apologist. We simply don't know enough to make a proper construction. And religion has tried at times to make declarations about whether the world was flat, when those facts really don't matter as far as religious discussion is concerned. For the most part, religion is about personal behavior, not scientific discovery. Of course, true religion is about all knowledge, but frequently the gaps between the disciplines are so large, we're not clever enough to bridge the gaps. It's akin the Hawking's Grand Unification Principle for physics, we're not bright enough in many instances to accomplish that which we seek.

Add to that, revelation is much more complex than we believe.

The reason we need apologists. . .
 

The reason we need apologists is because our Church seems to put so much stock in the "Truth" of the Church. It isn't so much much about the principles that are taught, but about whether the Church is "true". We are attacked because we claim to be the only true church upon the face of the earth. Everything is tied up in that one claim. If you attack that, then everything else unravels.

When I was at BYU I read an interesting interview with Sterling McMurrin in the 7th East Press (an underground newspaper that was promptly banned from campus after the publication of the interview). At the time McMurrin was a member of the Church Education System. In the interview he stated that he believed in the message of the Book of Mormon, but that he didn't believe the Book of Mormon was authentic. To him, it wasn't important whether anglels really appeared to Joseph Smith or whether Joseph Smith really translated the BOM from Golden plates. What was important were the teachings contained in the Book of Mormon.

Does it really matter whether the BOM is authentic or whether Joseph Smith was really a prophet? If our basic human values are dependent on the veracity of a religion, then we don't really own those values.