Gestalt, as defined by Lexico, is "an organized whole that is perceived as more than the sum of its parts." Is there a word that effectively conveys the opposite, that is, a whole being less than the sum of its parts?
EDIT (1): A potential example may be a large and varied range of overlapping sounds that itself forms a discordant sound, e.g. a variety of instruments played out of rythm.
EDIT (2): Another example may be a 'complete' square, or diamond in this case, formed from two "criss-crosses"(X's), the top and bottom diagonals of which meet one another. Think an individual square of a 'square mesh'. However this square doesn't have clean edges, there still being 2 small projecting lines at each vertice. Think a noughts and crosses board with significantly truncated lines directed out from the square, such that they are too small to be noticed. In this case a square is recognized, however the projecting lines are not, in which case it may be considered less than the sum of its parts.