I have absolutely no problem with a square house with a gable roof.
No, the term "matter of taste" is wrong; it is rather a "matter of perspective" - more precisely: of perspective distortion: a square has the same edge length in both dimensions - but if one of them is an eave side and the other a gable side, they appear unequal. A square base and a gable roof visually appears like a rectangular base. Interestingly, depending on the viewpoint and roof pitch, the dimension that is "longer" is estimated differently - but they are then supposedly recognized as "unequal."
It only becomes a "matter of taste" at the moment when the perception is influenced by the fact that the gable roof is associated with something traditional, and the hipped roof (= roof without a ridge, usually equally sloped on all sides) is fashionable.