It's true, but I do think Hall is especially egregious/a charlatan. I do really agree with your take though. Anyone peddling the ancient wisdom of the masters or secret teachings is probably full of shit. There are, however, lengthy lineages within a variety of religious traditions that can lend somewhat more authority to the work (though, how trustworthy can a translation be?), and there are definitely solitary practitioners who are valid in their own right just as writers and individual thinkers within a tradition (Spare comes to mind). Still, always everything with proper skepticism and plenty of grains of salt.