Imagine a group arriving at a trailhead to discover that access is closed. One person planned the route. Someone else assumed the opening hours had been checked. Everybody has an opinion about whose fault it is.
Before that argument gets comfortable, someone needs to ask what the group can do now.
Make responsibility specific
The organizer can acknowledge the missed check and find a legal alternative. Another person can confirm the daylight available. Someone can contact the people still driving over.
There is room for an honest review later. In the moment, specific responsibilities give the group a way forward.
Let others contribute
Taking responsibility does not require making every decision yourself. Ask who has relevant information. State what remains uncertain. Give someone else a task they can actually complete.
After the outing, change the preparation process: assign the access check, agree on a backup, and make the information visible to everyone.
An apology can matter. A changed habit makes the lesson easier to carry into the next trip.