But the DM should also not be expected to set up the entire world just from the point of the player fun.
Again, not saying to change the world to suit the players. Saying don't waste everyone's time with something pointless. If there's a dead-end, say it's a dead-end. But if you're going to start rolling dice and spending fifteen minutes in complex explanations of opening gates and climbing up slimy tunnels, then have a reason for it.