The problem with the idea of class consciousness is that it assumes that someone can know “true” consciousness, unaffected by any other material forces. This is simply not true. We are limited by our material conditions, and we have a very difficult time seeing beyond them.
It is common for Marxists in particular to act like, because they are Marxists and have a Marxist perspective, they can see beyond the current situation in an objective manner. This is wrong, but that isn’t to say that a Marxist perspective is useless. We just have to understand that we aren’t objectively correct.