The basis for science is observation. Theory follows observation, then testing both positive and negative cases to prove a theory to be true. Observing and analyzing sound quality and the equipment producing it involves many dozens of variables. While there are a number of known and measured variables there are many more not measured and fully understood. Ultimately in this very complex landscape observation is more time effective than trying to understand all the science, particularly as a part time hobbyist. Also, trying to use a few variables to explain sound quality is a just gross oversimplification.
On top of this you have differences in perception… from different skill levels. If you are new to assessing sound quality, then you may only notice gross differences in tonal balance and detail. As you develop skill, particularly if you do this in parallel with reading about sound qualities and then listening for the dozens of discernible attributes, you learn. You can keep learning more and more over decades. So, where you are in this development will change your perceptions of sound quality. Finally, we value different sound qualities differently.
So, while science is interesting (I am trained and was a practicing professional scientist for over a decade)… high end audio is primarily an observational pursuit if you are looking to put together a great sounding system. Thinking somehow that if an audio effect or cause does not have a confirmed scientific explanation and therefore is suspect or wrong is absolutely ridiculous. While a few gross effects on sound quality are easily scientifically explained, most are not… or are just not worth the Herculean effort required.
So observation is key and the more experienced and educated you are in it the greater will be your ability to observe and describe the effects on a system of different pieces of equipment.