Just a note: You need to check your own arrogance levels when you call something unwinnable.
You may not see the way to win, but that does not mean that 3, 4, 5 or even 6 other players putting their heads together can't come up with a solution you did not consider. Over the decades I've had entire adventures rendered moot by a creative solution of a PC. I could have fought the solution and forced it to not work with contrivance, but I learned to let the Wookie win and celebrate the victory of the group. I repurposed a lot of the material I prepared at other times, and continued on. Some of those situations were intended to be difficult challenges, but the PCs/players just outsmarted me.
Build the world that makes sense. Give your players and PCs the tools to recognize it fairly. Then let the story unfold.