Disagree. Some people are less self-aware than others. It's not a matter of opinions or what you believe in, it's a matter of how much you are aware of your own cognition.

There are many people out there who seem to lack the ability to analyze the consequences of their behavior, or to admit that they were ever wrong. There are also people who seem to be very bad at understanding what are their motivations for doing certain things. Not being able to look back at your own behavior and your own mistakes makes it nearly impossible for these people to grow.

I won't get into the argument as to whether these differences in self-awareness are biological in origin or due to nurture. It's probably some of both. Either way, even though this metric is multidimensional and hard to quantify, some people are definitely less self-aware than others. Just like some people are less physically fit than others.