I am an old, male boomer. I want to shout: I think the anti-millennial crap spewed by older people is utter bullshit. It's unfair. It's wrong. It's so horrible I categorize it as on par with full-on racism.
Millenial people (they are not 'millenials', some mythic creature in your imagination) did, in actual fact, grow up and come of age in a remarkably shitty time. Worse than other bad times, maybe yes, maybe no, but from 9-11 on, American society has not been good. This is compounded by their vicious exploitation by the ruling classes and corporations. You needn't go any farther than the elimination of art and music from public school, to the cost of college education and then the rapacious structure of the student loan industry.
But another thing that matured in the lives of millennial people is the technology of worker exploitation. The fucking over of young people in the job market is unconscionable. And, as with student loans, it's abetted by the government (though more on one side of the aisle than the other) supporting corporations uber alles.
Before networked technology, it wasn't practical to manage randomized work schedules that make you work days alternating with working nights. There weren't as many jobs simple enough that firing an experience worker because they are making an extra buck an hour and you can hire a new one for less. It makes your life miserable on purpose.
We won't talk about climate change, the unwholesomeness of food, or mass shootings every day, or etc, but they count, too. Suffice to say, I agree that things suck today and tell you that they are actual things that have been done, almost maliciously, mostly to young people.
I also think that much of it could have been avoided. I think the older peoples' condemnation of millennial people is mostly projection. They cannot face the guilt of having wrecked the culture and the planet so they blame the victims.
I start to say that I also apologize for my age cohort and it's bad behavior but, that doesn't capture my real feeling. I am enraged and ashamed of being part of such a rapacious, short sighted and prejudiced bunch.