Nobody and nothing is above criticism but when it comes to criticising people like Shakespeare it's very hard to tell what potential negatives are a feature of the context and time he wrote rather than something about him as a creator.
When it comes to people who are really brilliant criticism might sound like nitpicking for the sake of it. I find the kind of person who aggressively goes against the general consensus for the sake of making themselves seem like independent thinkers. I have a friend who has watched every Game of Thrones episode purely so he can keep telling me how shit he thinks it is. (I'm not saying that the OP is doing this by the way, it's just something that annoys me)
It's always worth remembering that your criticisms aren't above criticism either.
When it comes to people who are really brilliant criticism might sound like nitpicking for the sake of it. I find the kind of person who aggressively goes against the general consensus for the sake of making themselves seem like independent thinkers. I have a friend who has watched every Game of Thrones episode purely so he can keep telling me how shit he thinks it is. (I'm not saying that the OP is doing this by the way, it's just something that annoys me)
It's always worth remembering that your criticisms aren't above criticism either.