I think that millennials are simply led to believe that it is easier to advance because their parents had it that easy, but now the people at the top dont want to make way for the people at the bottom trying to move up.

I'm not sure I agree, maybe this is because all the millennials I'm familiar with spent time in the military, but we're used to being abused and under-compensated for things. Additionally, there's the pretty common experience of our parents, not advancing quickly, but having their livelihoods destroyed at a moments notice because of some brilliant "cost-cutting measure", usually involving mass layoffs, canceling of benefits, and being fired instead of retired to save on pensions. We know what bad leadership looks like, and if we don't trust you to be good management, you'll get the bare minimum. Bad leadership wants to: take away your family time because they didn't properly time manage, increase the scope of your responsibilities without pay because they don't want it themselves or won't hire someone else, will promise you advancement and then deny it to anyone but their cronies.

The complaint is: "That's part of the working world!"

There response is: "No, it's part of a shit company filled with garbage leadership with toxic people, and I can do better than you."

The emotional response from management is "They're ungrateful! Look how selfish and arrogant they are!" but the reality is that they don't feel like they have to take anyone's actual shit in order to have a good and balanced work/home life. Why should management obligate their employees to trust and obey them when they fuck their employees over? It's not selfish to think your time is valuable.