You're quite right that while the rich have gotten richer the poor have gotten richer too, just to a lesser extent. But it doesn't mean the poor are better off in every way. That's only true if we look purely at monetary wealth/purchasing power. But because we live in a society that gives a bigger voice to people with money, many people who are relatively poor can feel increasingly disconnected from a feeling of being an active participant in society.

The issues are broad and subtle with wealth inequality, too much for the scope of an HN comment, but I would posit that inequality issue are about more than access to goods.