One of the most infamous alternate history discussions I’ve had the misfortune of witnessing has been “D-Day On The Frisian Islands“. The author somehow assumed that landing the Western Allied invasion force there, instead of in Normandy, was viable.
(In short-there’s no room, and they’re within artillery range of the shore)
The author assumed the lack of planning for the Frisian Islands was anything but what it was-a sign that it was completely unworkable. Since then, I’ve taken possible military operations where nothing is written about it under the unspoken consensus that it’s a bad idea as “Frisian Islands Redux”.