That is incorrect, at least as far as I understand. I direct you to post #2,507.
one of the rules of the game is that you solve the puzzle with the tools at hand.
This seems to be an instance of
setting as puzzlebox - you use the word "puzzle", which I've also used.
On this I reiterate what I have already posted, which I think is also consistent with
@Hussar's posts: if the setting is a puzzle for the players to solve, why would they bother investing in it via PC connections, relationships etc?
I'm going to elaborate on my view on this by reference to something else you said in post 2507 - I'm not sure how much you meant to lean on it, and how much it was more of a throwaway line, but from my perspective it provides a nice illustration of and entree into my thinking on the topic:
Unless there is something very specific (I have a bag that can produce one typical item per day; oh, look- we need a ladder! Got one!)
Suppose the PCs want to climb the wall of the mayor's compound, and one of the players says "I look around for a ladder." How is this action declaration resolved?
If the parameters for its resolution are
the GM's notes plus
the players' equipment lists (including the rules for growing those lists by spending gold etc) then one upshot is a very thin setting. I live in an inner urban area, and it would be, for practical purposes, impossible to make notes listing every possibly salient things - tools, vehicles, loose cobblestones, overhanging tree branches, etc - for the 8 or so houses in my street, let alone the whole block or the whole neighbourhood. A pseudo-mediaeval neighbourhood won't have quite as many material goods, but will still have more than is feasible to include in notes.
Thin settings are handy for puzzles - the last time I ran a murder mystery RPG, I used pretty standard contrivances to keep the setting thin so that the players had a fair opportunity to acquire and reason with all the clues. But they are not settings that encourage the sort of investment and engagement by players that some posters (including me) find enjoyable.
So how do we make settings thicker? There are a wide range of options -
@Hussar already mentioned spending Action points; my overall preference is to have it check-based (Streetwise, Circles, Resources, etc) - but in D&D the default is freeform roleplay and negotiation between players and GM. And my view remains that there is no particular reason why the default answer should be No.
Is there a ladder around here? Maybe there is.
Do I know someone who works in the mayor's house? Maybe you do.
I wonder if one side is expecting the players to pull out the "magic background card" for almost any challenge, and the other side expects the players to be reasonable about it and it will maybe happen once or twice ever for each player.
I still stand by the following view: if every option in "the adventure" funnels the players to B, then getting to B is not a challenge. And so having a sister open the door to B; or having the GM just drop B into play using their (extensive) power to manage the background and frame scenes; is not circumventing any challenge.
As I posted upthread, the real issue for me is the risk of contrivance. But that's always a risk when the fiction is established by free negotiation. The solution is for people to be sensible. My personal experience is that most players don't like contrived fiction any more than GMs, and so won't suggest stuff that seems contrived.