Because most of the Shapespark scenes do not include such detailed high resolution objects, Shapespark default geometry compression parameters do not work well for them. By default Shapespark uses vertex accuracy of 0.5 millimeter, so objects that require smaller details will look ‘Minecrafty’. To improve this, please set the vertexAccuracy setting to some very low value, for example 0.000001.
This post explains where to set this value.