Yes, graphics were worse when we grew up (assuming same rough age) but we still looked at them and said "Wow so realistic!" so I don't think that the issue is that people now see realistic zombie films and think, great, I'll go stab someone on the bus for disagreeing with me.
I think its more the case that people are living in dangerous neighbourhoods, so they carry a knife for protection and are amped up ready to use it and so at the first sign of confrontation, they do. What used to be a fist fight is now a knife fight. What used to be a sore head is now a dead body.
But, I do agree with the poverty link. I grew up in poverty, I saw the lifestyle, the way people act, the way they aren't raised by their parents. It's been this way for thousands of years. It'll never change.
And I'm pretty sure this perfectly correlates with poverty. Both parents working means the kids are at home without supervision and with unlimited access to the TV and streaming services. In my childhood, it was still pretty easy to see that zombies were a movie invention, but with modern CGI, I can't tell the difference anymore.