It's perfectly good enough, but it doesn't mean that we can't subjectively use the word "natural" among groups large and small, to convey a concept that's meaningful within the group. As I said earlier in the thread, my best audiophile buddy and I have been listening to systems together for 20 years. When he calls something "natural", I know roughly what he means, and often tallies with my sense of "natural" too. This is a subjective response, I'm not for one second trying to suggest that it means anything in absolute terms, it's merely a means of communication of an idea.
Now, over time, and with experience of the views of others, it seems that this sense of the word "natural" extends a little further than conversations with my friend. It seems some other people use the term (not always, but often enough) to convey the same kind of subjective response to a component or system. That's it! That's all there is to it! Nobody is saying anything is objectively superior, or that it's reality or anything other than discussing a shared subjective response. Not everyone has to share the view, not everyone has to agree with these terms, but for those that do it's a meaningful expression that conveys information. That's all. Nothing expressed as fact, no absolute statements made, no disagreements about measurements or frequency responses or any other thing.
It struck me last night as I ate dinner that if I said one sauce tasted more "tomatoey" than another, many others might know what that means and share that view without the need to produce a gas chromatograph. It's an imperfect analogy certainly, but I wouldn't know the exact tomato or tomatoes that went into the sauces, I wouldn't necessarily care whether one was truer to the original tomato or not, but I'd definitely know which tasted more like some internalised view of the taste of tomatoes to me, and it's not unlikely that many others would find it matched their own internalised sense of "tomatoeyness" too. These things aren't well-defined, but they're not without meaning.