C'est always means It is. C'est is used to describe situations, actions, phenomena, and not a single word. For instance, Dire des gros mots, c'est bête et méchant = Saying bad words, it's stupid and nasty. The action is stupid and nasty, not a genderless it.
N.B. Be careful, the English genderless it is not genderless in French. For instance, when speaking about a table, you say it in English, but you say elle = she in French. It's because all nouns have a gender in French (La table is feminine)
English uses an "impersonal it" frequently, as well as a "dummy it".
The dummy subject is found in sentences like:
It is raining.
It is sunny.
It is cold.
In these cases, the "it" could be taken to mean the weather but that's not really the case. If you change to the non-continuous verb form, you get sentences like:
In January it often snows.
It always rains in April.
Back to the impersonal use.
It is a shame that he can't come
It is stupid to think he does not understand.
"John, why are you doing that? It's stupid, and it's naughty. Stop it at once!" The first two uses of it's are impersonal and apply to "the situation" or "the action(s)". The last, in Stop doing it could apply to a specific action previously mentioned, or to a continuing activity. Either way, it is impersonal and genderless.
I am a UK English speaker, and I have to disagree. The main meaning of mean is "ungenerous, miserly*, but there is a subsidiary meaning of "unkind, even spiteful" . It is not as strong in Br Eng as Am Eng "mean", which can mean "vicious, physically aggressive". There is no context to our sentence, so I would not choose "mean" but rather something that can apply on both sides of the Atlantic - "petty" perhaps?