Indeed, parenting is a big part of the problem. Many parents don't want to parent, they want to be friends with their kids and not deal with bad behavior.
There are more single-parent kids being raised today. There are more families where both parents work and their kids are left to raise themselves.
The internet and social media results in instant gratification that they then expect in the real world.
The kids are largely the result of their environment and it's very easy to want to blame the kids because they "should know better" but what if there was no positive influence to show them what that actually is?
This video is a good watch and may help see another perspective.
Another area of concern has to do with the "nature" aspect. There are some people, kids and adults alike, that have mental disorders that prevent them from being able to act rationally in certain situations. What may appear to be a "spoiled brat of a kid" to an outsider could actually be a kid that has a disorder where their "fight or flight" part of their brain kicks into overdrive and the logic/reasoning part of their brain cannot compensate. These issues are not the result of continuous bad parenting but instead are often the result of early childhood trauma or birth defect.
It's very easy to sit on your porch and judge everyone else, but unless you know what each kid has gone through or is living with then you can't possibly have any idea why they are the way they are. All you can see is how they respond in certain situations and many times there has been nobody around to teach them the proper way to respond.
It isn't the job of school teachers to raise our kids. It's their job to educate them. The kind of people our kids grow up to be is up to us as parents.