I think your viewpoint stems from your interpretation of 'condition.' Perhaps I'm mistaken, but you're understanding 'condition' to mean a layer of exterior factors that are applied on top of the essential human experience.

However, the word 'condition' is not at odds with how you'd like this area of study to be seen. If we take Dictionary.com's primary definition of the word we see it's:

Condition: a particular mode of being of a person or thing; existing state; situation with respect to circumstances.

And now if we take a look at the definition of 'the human condition from the opening of the Wikipedia article:

the characteristics, key events, and situations which compose the essentials of human existence, such as birth, growth, emotionality, aspiration, conflict, and mortality.

I'd say those line up pretty well and are far from 'meaning nothing'. Furthermore, the actual definition of the words 'humanity' and 'humane' don't really touch upon the ideas mentioned above.

You are right that language is vast and powerful. It is also abstract and indefinite. Words are only pointers to what they hope to describe and do not have any concrete basis in 'true' reality. As such, they can be twisted and re-appropriated to mean whatever a group of people choose. Yes, the words one uses are important, but using them 'accurately' comes secondary to communicating the essence of what you mean. Isn't that the whole point of a metaphor?

In this sense, 'the human condition' is more than a fine phrase for its intended purpose.