I can't speak for anyone else, but I offset things I had slightly ahead of time (the PIAT-style weapons, which were on use like three years later) with things I don't have (tanks, armored vehicles, gasoline-based ships). Sure some stuff is OP in comparison, but you also have to take into account weaknesses.

But it is important to remember this is a roleplay, not a strategy game. You cannot "win". The point is to create an evocative story.