Getting them to think and experience the game world rather than spoon feeding them with the results of a dice throw is kinda the point.
Yes, but even in the best campaign world, the experience of the player of the reality of the game world is like water dripping through a straw compared to the full immersion of reality. Reality comes in a 3-D full color high resolution 24-7 experience complete with surround sound, tangible sensation, odors and flavors. It's a place where you can truly live. The game world is conveyed in a handful of sentenses of prose, often hastily composed. The players are not experiencing the game world in the same way that there characters do, no matter how evocative your descriptions are.
At some point here, you've moved from calling me an idiot - which I don't mind at all - to insulting the mindset of everyone that disagrees with you by insinuation - which I do. I don't 'spoon feed' my players, nor are my players immature nor my games juvenile.
There is a point to text walls from time to time to try to convey some small percentage of the environment to the players, but breaking the pace of the game up by putting walls of text in front of the players all the time is going to seem contrived at a minimum and dull and bombastic at worst.
Personally, I find your 'clues' groan inducing.
Playing the game this way, I think, is much more intersting than a die roll and a simple statement of, "Your character has heard about these things before, and he knows that they shun fire."
Maybe; maybe not. First, it's not at all clear to me which way the encounter is more fun for the players. Figuring out that an undead monster might be vulnerable to fire doesn't constitute a particularly intriguing puzzle, especially for an experienced RPer who will probably try fire on undead based on game experience even if he doesn't pick up on your clues, especially if he has any reason to believe that the monster has some sort of physical immunity. For most gamers that have played more than a few sessions, pulling out torches and burning oil in response to any indication of 'your attacks don't seem to be working' will be almost a scripted response.
I'm struck by the fact that you seem to think figuring out a monsters combat vulnerabilities and defenses is core to the idea of 'role playing'. Personally, I find this tangental to the entire concept. I've heard of people who dislike the concept of skills like diplomacy, intimidate, and bluff because it interfers with 'role playing', but never before anyone who claimed that about 'knowledge'.
The first thing I want to point out about your position is that real game play is seldom so binary as this. There is no reason at all you can't both use knowledge checks and provide clues. If the characters have the skills and luck to have heard about Leather-Skinned Ghouls and thier vulnerability to fire, then fine, but if not, if the players have the perceptiveness to pick up on the clues provided and creativity to use them then that's good too. If Leather-Skinned Ghouls are common pests and foes in the world, then there is no reason to hide their characteristics and try to make them mysterious. If on the other hand, Leather-Skinned Ghouls are unique to the Lost Tomb of Gaftek the Obscure, then there is no reason that mundane knowledge and lore would provide a description of their unique abilities. Likewise, while mundane knowledge might provide you with the general characteristics of sprites or goblins, it won't tell you that this one is a 4th level sorcerer with a fondness for fine wine. That sort of knowledge has to be gained by searching about for clues in the environment or interaction with the creature in question.
The second thing I want to point out is that in most cases in my game, knowledge is not used like a passive ability. Sure, you get a 'passive' knowledge check when encountering some things, and with success you get a some amount of things you know about the situation. But most of the time the point of knowledge is arbitrating player propositions. Regardless of what information I 'spoon feed' to the players (as you would have it), players are still going to want to know more about their situation. This is true both inside and outside of combat. In effect, in every game session I've ever been in, players will ask for clues. This form of asking can take the form of saying things like, "I want to examine the painting on the wall more closely." or it can take the form of saying some thing like, "I search the drawers of the desk." Whatever the form of the proposition, the meta-proposition is effective, "I want to prompt you to say something about the situation that provides me a clue what to do next." That clue could be anything. It doesn't have to be something like, "You find the drawer has a false bottom." It could be something like, "The drawer isn't as deep as you would expect it to be." But both are effectively 'clues' or 'bread crumbs' provided to the player that give the player some indication of what future propositions might be rewarded with more clues and hopefully eventually affirmation of success.
So the more usual use of knowledge (and most skills really) is to arbitrate in something less than an arbitrary fashion whether the player succeeds in gathering a clue based on the character's ability (rather than the player's alone).
I've argued elsewhere that RPG's must be primarily about testing player ability. But if RPG's are only about testing player ability, they aren't really role-playing games in a general sense because by definition a game in which only the player's ability is tested and not his character's ability is a game in which you can only play yourself. Your character knows only what you know, and has only your judgment, perceptions, and social accumen. If you do away with diplomacy as a skill concept, you end up with a game that is solely about using your own charisma to convince the DM - which is therefore subject to the DM's own preferences and biases (and relationship with the person doing the convincing). This is from the perspective of the player's wholly arbitary. The DM decides everything according to his whims. The DM doesn't feel his whims are arbitrary, but that's the DM's perspective and you have to be very careful when DMing not to see things only through your own eyes.
At my table, you can't ask for a diplomacy check directly. A social skill check must be earned through appropriate role play. Whether that diplomacy succeeds is arbitrated in part (though not completely) through use of the dice. Really reasonable requests can fail when made by characters who are in game terms inept. Really confrontational and tactless approaches can succeed when made by a character with great charisma. A player can't completely substitute his own charisma for his character's. I tell my players that I judge their approaches based on the content of the approach, not the smoothness of the delivery or the elegance of their words. I let the dice handle the randomness and unpredictability of the world.
Knowledge skill checks serve much the same purpose. The player asks me a question about his character's understanding of the situation. Rather than arbitrarily deciding what his character knows, I give the character a chance of knowing some random factoid that itself serves as a clue. That way the player isn't completely dependendent on saying 'DM pass phrases' before I provide entrance to the next portion of the scenario and give them the next bread crumb.
That is actually role playing in the sense of being able to take on a persona other than your own.
