That's the whole point. When people hear "the middle class is shrinking" they intuitively believe people are slipping down a rung and joining the ranks of the working poor. The data doesn't back that up. The middle class is shrinking, but more people are moving up a rung than falling down one.

Which isn't to say that you're wrong about wealth inequality increasing. The share of wealth controlled by the ultra wealthy IS increasing, but the specifics of how that is playing out are nuanced and, at times, counter-intuitive.