It was an incredibly stupid plan, followed by even more stupid decisions:

• Jon: “We need to mine dragon glass and make weapons to fight the army of the dead,” but not one person has a bow with dragon glass arrows. Only Jorah has dragon glass knives.
• To capture a wight and then escape the Night King, you might need something that runs faster than the undead. Horses, anyone?
• Instead of having Gendry run a marathon, take a couple of ravens with you, saving hours and making it a little more possible that they Dany could save the day without beaming down to Eastwatch.
• Beric could use his flaming sword to keep everyone warm and later on melt the lake around the island
• Jorah: “if we kill t he Night King, the whole army will perish.” Jon: “No, we’ve got to get the wight back to King’s Landing.”
• Jon tells Dany to escape instead of having the two remaining dragons destroy the Night King.

My biggest disappointment was the throw-away death of Thoros, which served absolutely no purpose other than to take away the chance of resurrection (until Melisandre conveniently comes back).

It would have been so much better if they captured a wight and returned to the Wall with a seriously injured Jorah. Upon passing through the Wall, the wight would disintegrate as shown in the episode when the wights entered the Three-Eyed Ravens’ tree-cave. The heroes are crestfallen because the stupid plan failed, and are saddened even more by the death of Jorah the next day, who then becomes the wight they bring back to Daenerys.