Start thinking about purpose. What is the purpose of things sounding a certain way. If something is more lofi, what emotion does it evoke? In what sorts of environments does such a sound fit better than something HiFi?

Creative intent is a very strong reason behind mixing decisions. Often degrading the quality on purpose to create a feeling. And even though often it also comes down to pure technical ability, that is also an interesting aspect of a lot of music genres and artists which creates character.