That I disagree with these ideas is putting it rather mildly.
In my conception of the game, play is a volleying of ideas between players and GM, with each both reacting and acting upon each other. The GM’s responsibility is to give sufficient context for the players to make meaningful choices, and then to present the consequences of those choices as new context for the next volley of player choices.
The fictional campaign milieu, however it is devised, and including its inhabitants, is the primary context that players have. The ruleset is the secondary context, with the players presumably understanding that the rules are a model of the world, and can be altered as circumstances demand to model the world better.
Now, it has been said that “necessity is the mother of invention”, which is another way of saying that creativity often occurs as a reaction to some problem. Far from restricting creativity, having something to react to often increases it. Consider all of the novels, poems, songs, paintings, films, etc., that are specifically inspired by, or reacting to, something else. Now, consider all of the same that develop in a vacuum, reacting to nothing. I cannot think of a single example of the second set.
Reaction need not be creative. You can react – or act, for that matter – by rote. But reaction is not intrinsically less creative because it is in response to something else. In fact, the reason why simply watching a movie is not generally viewed as a creative process is because it is passive. You do not react.
If, on the other hand, you watch a movie, and your reaction is to feel that you could do better, that is creative – so long as you actually go out and do it! Edgar Rice Burroughs claimed that he started writing as a reaction to the novels that were then available. No one was writing what he wanted to read, and he thought he could do better.
So, imagine that you wanted to slap White Plume Mountain into a sandbox campaign milieu. What to do? Well, first you need to remove the intro parts that refer to how the PCs get involved. Then you need to go through the module and change anything you think should be changed, so as to fit the campaign milieu. Then you need to place it somewhere. Then you need to decide what “footprint” it has on the local area. You may also have to update it from time to time to keep up with campaign events.
Me, I would place the theft of the three great weapons into the far past, and make mention of White Plume Mountain early on. The players can either decide that they want those weapons, and decide how to go about it (at any level), or ignore it, or do whatever else they like. The presence of White Plume Mountain removes no agency from the players whatsoever.
Some players may choose to tackle White Plume Mountain “because it is there”. Well, that’s a meaningful choice, too. It is as meaningful as choosing to raise an army, create a great collection, or waylay travelers in a forest.
Please take a moment to read this “module” “that shatters the illusion that the DM ought to control the events of the game”. Were you under the effects of that particular illusion? Reading this blog, do you imagine that I am?
Nothing in the "module" is in any way invalidated by the inclusion of White Plume Mountain in the GM’s prep work. Conversely, though, the GM’s prep work may be made considerably easier by the module’s inclusion, and the module itself might carry resonance with both GM and players who have heard of it. Some GMs create campaign milieus modeled off of real world history to create exactly this type of resonance.
Prep work is not part of playing the game. But it is part of the game. Creating dungeons is no more self-indulgent wankery than is creating maps of a fantasy version of Europe for your campaign, devising trade tables, or devising means to randomly determine resources. Nor is the purpose different – in each of these cases, the GM is attempting to create a context in which meaningful choices can take place. And this has nothing to do with keeping players on a chain, or a paternal “father-knows-best” attitude.
Prep work is not play. You can include anything that strikes your fancy in your prep work, and it still will not be play. Prep work cannot make decisions for players. Prep work cannot railroad. Until you sit down at the table, with actual players, it is not play. Prep work commits no sins.
And, if I was a player presented with the afore-linked introductory “module”, my first question to “If this part of the world isn't your cup of tea, strike out for warmer seas, or jungles, or deserts, or polar climes” would be, “Cool. Where are we now?”
Because it has to be.
The GM is my character’s eyes, ears, nose, sense of touch, and taste buds. The GM supplies my character’s knowledge of the world and of history. Until the GM has presented something, how can I make any meaningful decisions?
You know where the monsters are - you do not need me to tell you. The monsters are in the wilderness, they are in the mountains and hills, they are at the bottoms of lakes and lagoons, they are in caves and at the bottoms of ravines, they are in the sewers of the largest cities ... and well you know, where there are monsters, there will be treasure.
No, actually, I did need you to tell me that this world includes monsters, mountains, hills, lakes, sewers, and cities. And, if the kind of campaign I want you to run includes hacking and slashing them, I need you to tell me what I can see so that I can find those things. I need you to tell me what I know of the world so I can do the same. If you set your campaign in a fantasy version of Europe, perhaps you did so just to avoid having to overtly present that information, but you are dreaming if you imagine that you are offering nothing other than a blank slate.
And if you are offering nothing other than a blank slate, it might be preparatory to a role-playing game, such as a session or sessions in which the parameters of the game are devised by the group, but until there is context, there is no role-playing game. Before context, there is only prep for the game. Group prep, solo prep, whatever - it's still only prep.
If you prefer to play something more 'civilized,' let me remind you there is an entire world of crime open to you. Become murderers, become arsonists, become racketeers or smugglers, examine for yourselves all the dark arts of flouting the law and living fast on your feet for fun and profit! Or if that seems immoral and undesirable, consider the possibilities to be found in catching criminals. Bounty hunters are always in short supply and the act takes courage and inventiveness.
Then again, perhaps collecting other things strikes your imaginations better - rare objects, books, art, magic items, what have you. Create a library, create a zoo, travel the world wide gathering together all you need to make it the greatest ever. If you seem in short supply of ideas, there are always mages aching to make your acquaintance, to pay you hard coin for things they know they need and know where to find.
All of this is context. All of this is the GM presenting information about the world, so that the players can make creative and meaningful choices. Pretending otherwise is pure hypocrisy….especially if it is pretending otherwise so you can weep over the people who don’t get that this is a game in which you can do anything. D&D (or DCC, etc.) is not about solving mazes or puzzles, but solving mazes and puzzles can be a part of it, if that is what the players desire. Remember “I'm prepared to run any sort of game you wish”? The world is made neither larger nor smaller by one mountain being called the Omu Peak or by another being called White Plume Mountain.