Complexity is the enemy of Happiness.
For 280,000 years, humans were "happy" because their Biological Feedback Loop was closed. The Ape Logic, If you are hungry and you find a tuber, your brain floods with dopamine. If you are cold and you find a cave, you feel "bliss." The Problem, modern humanity has uncoupled effort from reward. We have the "peanut butter" (the resources) without the "swing" (the freedom/play). We have "too much," so our brains have to look over the fence to find a new metric for success.
A human 20,000 years ago staring at a fire after a successful hunt was likely experiencing the exact same neurochemistry as a modern person winning a promotion. The "quality" of the happiness doesn't change—only the cost of the ticket. Back then, the ticket was a spear and a long walk. Now, The ticket is 40 years of "dangerous social operations" and "detachment."