lol are you seriously telling me that when you go in a store, pick a volume manga, the only thing you look is the front cover and nothing more, you don't look at the back? the synopsis of the story is there.
I'm not overestimating people, i'm just telling the basic of what a person would do when going to buy manga, they will see the cover of it in a store when going to buy, give it a look, look at the back of the cover, read the synopsis or just give check in their phones and instantly knows what is about, and that's it, if you would not even look at it because isn't the kind of story you would be interested, that's you, that doesn't mean the rest wouldn't, also you're giving too much power to a cover, they're not that crucial neither have the power to sink or turn a new series into a hit, i honestly doubt that anyone will just buy this knowing zero context about the story and think "oh my God, they fooled me, i thought was a calm slice of life about a dude in a island, dropped!"
In my personal opinion the combination of the illustration, with the title and Tamura's name is enough to people at least pick it up and give a look in the stores.