I'm not a design expert or necessarily even design literate. Stating up front: I understand the importance of design and think it's a super important profession

I'm not a design expert or necessarily even design literate. Stating up front: I understand the importance of design and think it's a super important profession. If anything, I'm envious of people who have the ability to practice good design. I have to say that when I read stuff like this it kind of scares me away from trying to become fluent enough in design to practice it, because of where subjectivity seems to hide. I think I understand the principles of contrast, hierarchy, balance, scale, feedback, etc. in theory, it just seems very difficult to holistically judge a design that may be emphasizing different attributes to achieve these characteristics. Take the complaint about button weight: > Where thick, dark borders and arrow glyphs used to bulge the buttons toward one’s eye, the buttons now “weigh” so little that to distinguish them is a chore. The same goes for other buttons throughout OS X. The borders may appear lighter in the displayed photo, but how can I judge contrast without seeing the contrasted element(s) (i.e. the surface on which the buttons rest, the positioning from other UI elements, etc.). Also in some ways, there seems to be more contrast in the new buttons. For instance, the button shapes seem to contrast from each other by not being cutouts of the same rectangular shape. Perhaps that's the only contrast that's really matters here, since another form of contrast may be in place to distinguish this button group? Similarly the discussion about drop shadows is difficult for me to grapple with. What are the drop shadows on the dock doing for me? It seems like a drop shadow is useful for distinguishing mutable elements (UI controls) from static content, but the dock only serves to launch applications. As a user of Apple products for years, I'm innately trained to understand this, but perhaps this is untrue of a first time macbook owner? I understand that experimental design to test these kinds of things is very difficult, but perhaps it'd be a more convincing argument with some supporting evidence. Or take the complaint about feedback with the "New Folder" button in Notes. It's true enough that there's no visual feedback on the button itself, however when you click the button a highlighted text field appears above, waiting for you to enter in the folder name. I sort of understand this complaint, but when I tried to play devil's advocate I came up with the explanation that the feedback was actually drawing attention to the next task I needed to do (i.e. naming the folder) instead of the button itself. Which way of seeing this is valid? I feel like these kinds of conversations are very interesting and important for making design decisions that benefit the largest number of people, but it seems like the conversation often relies on subjective judgements on design elements that could be argued either way.