Here's the way I see it:
True equality can only be achieved when everyone is exactly the same. But that's boring, right? There are probably about 50 million books that I'm sure we all read in high school about a hypothetical society where everyone's the same. The problem is, we want it both ways. We want equality, but we also want diversity, and the two things cannot coexist.
So really, when we talk about "equality" in society, I think of finding a happy medium between equality and diversity, rather than true equality.