One fascinating thing about real history is the nature of knowledge. I was having a big nerdy talk with a friend today where she was recounting some history about ancient classics that had been lost and the variety of really interesting people who recovered some of them and what that meant. It's the kind of history that's instantly recognizable because, well, nerds are always nerds, even in the pre-renaissance. 4chan has nothing on classicists bitching about each other's Latin translations.
This seems like it should be really gameable, but there's weird barrier that I have never really found a solution to. The problem with the history of knowledge is that it's full of questions we have already answered. That is to say, the discovery of an ancient greek text that lays out atomic theory along with its philosophical implications doesn't really get the pulse pounding (unless you're already a certain type of nerd).
This is a subtle reason why magic (or weirdness) makes for an easy out in a lot of settings. Magic allows for secrets which have no real world analog, so we can accept it as jarring. Eldritch horrors, vampires in the shadows or secret UFO landings provide us a means to have Big Meaningful secrets without much in the way of understanding.
And maybe that's a necessary shorthand. If you're going to assume minimal setting buy in from players, then you want secrets that carry their own weight without needing context to give them meaning. Tentacled horrors are an easier sale than the invalidation of heliocentrism. The former can drive action, the latter not so much.
But the problem is that this model ultimately produces thin, brittle secrets. Monsters in the shadows? Other worlds than these? Elder horrors? These ideas and more all so digestible that they more or less transmute into tropes at the moment of their creation. It is only through the addition of context that they grow richer, but that tends to require enough work that it more or less undercuts the original point.
Which brings me back to those mundane, boring secrets. The trick, I think, is that what makes them fascinating is not so much the secrets themselves as all the things and people around them. Consider that in a world before the printing press, every piece of data transmission is painstakingly handcrafted. The power of the secret is as a thread that ties people together, specifically the people who are smart and driven enough to be really interested in this stuff. As with so many things, the really cool things can be found in the people.
Still, while that provides some motivation for more real secrets, I'm not sure that provides much in the way of guidance for making them any more playable. But what it does suggest to me is that maybe it's worth the extra work.
 - Ok, there's one solution: have Ken Hite at your game table.