Since every reviewer has a different setup and all of us have different setups the variations are endless and so are the subjective outcomes.
@tom2015 That’s exactly why making relevant product comparisons is absolutely critical. Humans are inherently awful at analyzing things on their own, but we’re very good at identifying relative differences between two things, and it’s these relative differences that provide extremely valuable perspectives and insights that better reveal a component’s sonic character. Without that perspective I completely agree with you that we’re left with highly questionable subjective opinions as there’s no check and balance to keep the reviewer honest. As an example, many’s the time I was well into reviewing a product and thought I had its sound nailed, but when I substituted another component for comparison almost without fail I’d realize my compass was significantly off and I had to reassess the component under review. It’s a very humbling and time consuming process for a reviewer but absolutely necessary IMO to be able to write a more accurate and useful review, and that’s also why I suspect publications like TAS, etc. refuse to do them. Just my take FWIW.