inb4 the "it's totally not a harem!" fanboys. j/k, we don't really get that type here.
As an example of "the exception that proves the rule", I called it a harem on another forum, pointing out that Sora is the only male character of any note, while there are a ton of girls - and they basically only interact with him, not each other. Some objected, and pointed out two male characters I'd overlooked - the grandfather of the pricess, and the god character that's introduced in the first episode. Now, if the only mentionable competition to the MC for girls' attention are an old man with a beard like Gandalf and a disembodied spirit who never interacts with the girls, that basically proves the rule.
EDIT: For that matter, what do the girls think of each other? Even Shiro, supposedly the co-MC with Sora, what does she think of the other characters? We basically have no idea since she only exists through her interactions with Sora. Sora is the only one with any characterization or interactions with more than one other character, and he's pretty one dimension even so. All the effort in the writing was setting up the elaborate puzzles set-pieces, not writing clever characters, dialogue or plot.
The "plot" is basically laughably bad, linear and predictable. It's like it got stuck in it's own formula from page one. Lolis play in the bath. Then Sora wins some elaborate game. The he alternately gains a big-breasted vixen or another loli for his harem. Then the lolis soap each other up in bath again. Then there's another game. Rinse and repeat (in the bath with the lolis). The whole meta-story is about how the world is a chess game, and he has to win 16 chess pieces to conquer the world. And he "never loses" - that's actually the catchphrase, so there's never a situation that challenges the hero, and he just gains the chess pieces in a linear fashion while gaining another loli admirer each time.
And in 12 episodes they get through 2 chess pieces out of 16 worth of conquest, so at that rate it's going to be a repetitive formula for another 7 seasons if they ever go on with it. And it already got into a massively predictable rut in the first season. Are they really going to animate the next 14 conquests interspersed with yet more loli bath time?