It isnt that, the issues come from ridiculous comparisons. Someone else said it on another thread I think. The initial though of Ivan Ooze is fair enough but when people are actually saying he looks like him that is just stupid because he doesn't at all.
Like The Guard said, the costume clearly takes lots of points from the character throughout all his iterations yet because Isaac isnt 8ft tall and built like a tank, or because he doesnt have black or dark lips (which actually arent the colour of his lips in the comics) people still have issues about him. And that is what is silly. It is fair enough that people don't like the costume but having something critical comes with something to back it up, not just flaming the Ooze card or the Not accurate enough.