Incorrect « il est » is used to mean "it is" if the it in question is a specific adjective. since the statement is not directed at a specific person, « c'est » should be used instead. for example, « jean, il est mauvais de trop dormir ! » is correct, because we are speaking to jean directly. in this case, we're talking about it generally being bad to sleep too much. the correct sentence would be « c'est mauvais de trop dormir »
