If the main text of a religion isn't a reliable guidebook to that religion, how can we determine if anything is?
Obviously, we can't.
What made you think we could?
All major (and most minor) religions present huge diversity. Within Christianity, the bible is taken as everything from vague metaphor to the "inerrant word of God." The Koran for Islam, the same. Buddhist practice ranges from meditative to non, from vegetarian to non, from rigidly scientific to the most laughable crystal-gazing nonsense you've ever heard of. New agers.... that's a basket so broad I don't even have a clue as to what it really means, although I have to say, I've rarely come away from someone's description of their new age ideas thinking "wow, that made sense." OK, actually, never. But I figure it could happen. :)
In addition to actual sect differences, there are practitioner differences, and they range all the way from non-believers who are there for the social aspect, to rigid adherents to every jot and tittle in every book (and some, like the Catholics, have quite a few books.)
For my part, I figure, if I want to know what someone thinks, just ask them. Unless I have specific relevant evidence, I don't assume people fit into standardized boxes. I have found that to very rarely be true.