I agree with most of this.
Though I wouldn't say it's a chicken or egg case regarding who became disloyal to who first, ie the worker or employer.
The millenials grew up watching their parents or other older people get canned or screwed over by companies, despite their loyalty. Back when people could be employed by one company their whole life, provided they did a good job, they had more loyalty to companies. Now that everyone knows that most companies don't care about their employees, most people have become mercenaries.
I read an article about a worker, who worked at IBM. Worked there for 30 years. Died of a heart attack in his 50's and was a few months away from being eligible for a full pension. He left behind a family and naturally they did not receive the full pension, they only received a vastly reduced pension that he had qualified for up to that point. A corporation really only has loyalty to it's shareholders and millenials are aware of this to an extent that other generations were not, so they don't feel they owe anything to a company.
I agree that good, skilled workers can move up fast now though.