Not all words in language have the same level of abstraction, some map on concretely to the physical world, other words point to concepts that are far abstracted from the physical world and really could not exist without language self-referencing itself. So there is a very large difference in the extent to which words are influenced by subjective context rather than reference to a tangible physical event or object.
If I define "good" AS a personal evaluative belief or prescription for an outcome, where is the logical problem here? If YOUR "good" differs from mine, essentially what we are saying is that we have different desires for the things that we want to have happen.
It's like , we can't have a conversation about desire because we don't have the same exact desires and so we can't even know what the word desire means. No, we have subjective desires and yet we can still know what we all mean by the abstract concept of desire, just as we all have different beliefs about what specific things are good and yet we can still have a concept of goodness