I dont know why people keep saying this. the MANY FPS WWII games are proof this isnt true.
It's like they never sat and considered how many copies of the various Il2 (1946, CloD, Stalingrad, Moscow, Pacific etc ) franchise are sold. Millions and millions.
Battlefield V has sold 8 million at least in the first few months. That game has it's own problems, but it isn't due to lack of interest in a WWII theme. There was intense interest and anticipation of a good WWII game.
It's like they think each of the million and millions that bought Rome:Total War were all PHD candidates in Ancient History.
It's not that anything needs to be improved, it's just that kids nowadays are lazy! And they should GET OF MY LAWN!
[Addendum]
Hitech has stated a while back:
In the last 100 days aprox 40,000 people have installed Aces High
I'm quite certain these people knew they were downloading a WWII game. It would be ridiculous to think they thought they were downloading a Space shooter.
There seem to be plenty of people willing to give a WWII game a chance. It must be other things about the game that is not convincing them to stay.