I think this is hyperbolic. Obviously the books are not "for all intents and purposes, completely useless" because people, in their millions, have been and are successfully playing the game such that they invest considerable time, energy, and money into it. I offer the premise that most people who continue playing the game do so because they find it fun. Though, as you allude to with your last point, it may just be that the game is addictive (I think it is probably both, to varying degrees).
To use a somewhat dissimilar example: I don't particularly like Counter Strike. Well, I hate it — it's pretty much the exact opposite of my platonic ideal of the first person shooter. I do still play it and
enjoy myself from time to time. With my friends. Because I enjoy spending time with friends.
Counter Strike does
nothing for me, the experience is made by people who I enjoy interacting with.
The example is dissimilar, because Counter Strike is, well, a designed game. Probably a well-designed one, it just so happens that I prefer jumping around like crazy rather than stopping to take a shot, but I still can feel the designer's hand, every aspect of it is carefully crafted to deliver a particular experience.
D&D isn't like that. It leaves many decisions that should've been made by the designer to the players (or, well, one particular player) — they have to basically finish an unfinished game.
Counter Strike doesn't expect me to design my own gamemodes, weapons and maps. And if it did, the fact that it turned out well/horrible would be asinine to attribute Valve —
I designed it.
Well, if we pretend for a second that Counter Strike isn't a videogame, which needs to be programmed, modeled, animated and all that.
I don't really understand your point about not knowing what enemies your sword will encounter - to me that is a feature, not a flaw. You prepare as best you can and then something else happens instead. Such is life. It's thrilling.
Let's say I'm running a D&D game you're playing in and I decide that it's my setting and there's 1st Regiment of Tarrasque Cavalry behind every corner.
I have this authority. PHB says the rules are just guidelines, DMG stresses over and over that Challenge Ratings and stuff are guidelines. You can't say boo to that. You, the player, know that a sword deals D8+STR damage, the designer chose that number, but does it matter?
I ain't breaking any rules. Yet the campaign still sucks ass.
OK, maybe I'm not that cartoonish. Maybe I just suck at encounter design, and there's an unfair TPK every two sessions, even though I'm actively trying my best to avoid that. It just so happens that my best is actually not that great. You, the player, know that a sword deals D8+STR damage, but does it matter? I ain't breaking any rules, yet the campaign still sucks ass.
OK, maybe it's the opposite actually. Maybe I'm spineless, maybe I really like your characters and can't find it in me to hurt them. You, the player, I ain't breaking, campaign sucks ass.
OK, maybe I'm a goddess among mortal men, the campaign is awesome, combats are cool, the story is thrilling, my descriptions drip with atmosphere and you will tell the tale of great magnificent Alice Zhu, Queen of D&D, to your grandchildren with a bated breath, this campaign will be forever ingrained in your memory, long after you forget what year it is. Was it because of D&D, of brilliant design of WotC, or was it because of me?
Isn't it interesting, if accidental, design that people with diametrically opposed views on how the game should be played can still play it and have fun?
That is my point: it's not the design. It's utter lack of it.
People don't have fun because D&D is fun. People don't have a miserable time because D&D is miserable.
People have fun because the DM did WotC's job for WotC well, and made experience fun for the players. Or failed miserably (which is understandable: game design is hard, actually) and everyone had a bad time.