I agree. It’s a huge topic.
I think there are some facets that could be broken down in an informative and reasonably objective way. I tried to . . . weave . . . some of that into this response about longevity: What’s the best string these days - #29 by hsb
There is a ton more related to different fibers, how they are processed into thread and the potential influence of the resulting physical properties on string characteristics. Some of this is knowable in a general sense that could be useful. Even if it wouldn’t tell the whole story about how string A performs or compares to string B.