You should be able to get 88% warscore if my math is right, or 89% if you wait for their war exhaustion to tick up another point. That is 88% of what you would can take if you siege down the entirety of England, England's allies, stackwipe the entire English army, and destroy the entire British fleet. Considering that you pose no threat to England proper or English trade, this is not unreasonable within the context of the game's mechanics.
Looking at the issue from the opposite perspective, even if you could land in England, the game prevents you from taking all of the English possessions on the continent. In relative terms, the warscore you can take seems fair, and arguably generous.
Looking at the issue from the opposite perspective, even if you could land in England, the game prevents you from taking all of the English possessions on the continent. In relative terms, the warscore you can take seems fair, and arguably generous.