It's because young voters don't remember the '90s and can't contextualize her record. They also don't understand how the world existed per-internet, or just how long it took to get something like gay marriage done.While I need to look at exit polls more closely and compare results from 2008 and 2012 at a county level, I think the focus on the white working middle class has overshadowed Hillary's poor performance among minorities.
No one should take exit polls for face value, for reasons the New York Times outlined, but as with election polling, +-3 points is likely within the actual result. Taking that into consideration, she did significantly worse than Obama in 2012 with minority groups as a whole, only those who do not consider themselves African-American, Asian-American or Hispanic staying about the same. This was especially true for Black men, Latino women, African-Americans under 44 and Latinos under 29. What I'm wondering is: was it because of Hillary or her message? Black men and Latino women votes shifted more third-party than for Trump. The same is true of African-Americans under 44 and young Latinos.
This falls in line with the general shift of young people as more liberal, but less D, more I, over the past 4-8 years. It's a big issue. Radicalization- not just happening on the right.