The point is that middle class used to be able to purchase enough for a family...a family being something of critical importance to phattonez's view of national economic stability, happiness, prosperity (etc., correct if wrong obv. phattonez).
It has steadily declining, while higher income has been taking those gains.
But globally we also look out of sync:
What your argument doesn't seem to include, is how that value is determined, and what negotiation position an employee is in, vs employer.
Unions are one way power used to be added to balance out labor.
Laws do in some ways (min wage, overtime, health insurance, etc.).
Also, government policy, leadership, educational support, education quality, rural outreach, etc., etc. There are countless factors that contribute, and a near infinite number of ways this can be slowed or even reversed.