First, it matters most what team you're on at these big companies. There are definitely teams that are more chill, and you better believe there are great managers that care about you. But many don't, and often teams that are "high impact" (i.e. move the needle on growth by owning the signup funnel) are more intense.

As for FAANG, Netflix was known to be the most laborious, although the best paying; They'd slash the bottom x% every cycle. Apple was known for being secretive and siloed, and because of their shipping cycles many teams can have intense overtime, but overall it seemed ok. Amazon in general sounded like a half a tier lower in terms of pay and work culture. Google and Facebook were often similar on most fronts and generally pleasant to work at, although I did hear Google's promotions were more bureaucratic.

In terms of "a new way of treating employees", well yes they achieved that. Outside of silicon valley have you heard of those flexible hours, rest and vest, unlimited free food, arcades, swag, best equipment, or even well-documented formulaic promotions? I remember telling my friends and family for the first time and without fail their jaws would drop. That's why most people in the world would love to work at FAANG still. You better bet those thousands of employees are very much happy there. These practices have spread by way of tech startups, but are still not "common" by any measure.

Anyway that's my 2c, I worked on a very pleasant team at FB.