User blog comment:DE-Note/RWBY Game idea/@comment-32598036-20150804014542/@comment-10380701-20150806073928

Going from it from a programmer standpoint, any engine will work. Even an ultra-realistic engine like Unreal or even FOX can be turned into moe moe animu with just clever usage of cel shading and models. Just because the most common thing seen in there are realistic graphics doesn't mean it's the only thing possible.

While the US is busy making their hyper realistic Nathan Drake, Japan is busy exploiting the more unused aspect of Unreal and gave birth to Guilty Gear Xrd's pseudo-2D visuals. This now started a growing trend of pseudo-2D games using full 3D assets, with the next in line being Bloodstained.

At that point, the main problem will be for the programmer, instead of the artist, since the artist is gonna work with lesser polygons on account of having simpler models. Meanwhile, the programmer has to create the custom shader. And shaders are a fucking bitch to do.

Grimm Eclipse operates on this idea, as Unity doesn't have a built-in cel-shading code, so Scott likely programmed a (or based it on another) custom shader to replicate RWBY's visuals.

So really, the only limit with engines is if you know the programming language to make it do what you really want.