Are you sure those things you listed - musicianship, originality etc. - are actually the things that explain why you like the music you like?

I found that I had to create new categories, and sometimes redefine a category, to make sure it was capturing something that wasn't common to all bands and to make sure all the categories were distinct and objectively measurable to at least some degree. (For example, "lyrics" might seem totally subjective but a band that just sings about girls and partying will probably get a lower score than a band that sings about more sophisticated ideas.)

There's a psychological tendency to come up with an explanation for our feelings when we don't honestly know the deeper reasons behind them.

Yup. This is a well-documented aspect of the psychology of decision-making. If I expand my spreadsheet a lot and it still has no predictive power, then I'll have to conclude that my tastes have no pattern and are based on my idiosyncrasies.