Voted "other." Focusing on modern western culture.
If I had to say one thing, it's a lack of (good) purpose. At all levels. Of course, I could be biasing this off of my own experience, but I think this is ultimately true.
The "god-shaped hole" in your heart is a real thing. I'm not advocating for religion. I can't bring myself to believe. But humans need
something to believe in. It gets them up and makes them do more than simply keeping themselves alive. So, what do we fill that hole with?
God was an easy one: 'this life is just a temporary tryout for eternity of either awesomeness in heaven or shit in hell beyond your comprehension'. If I can believe in that, I'm sure as shit going to do my best every day and try to look good for God. Problem here is as we access to more and more information about the world it becomes way harder to actually believe, and people don't.
Working for a better life for ourselves and family. I think about post-WWII, and the "leave it to beaver" era of america, and I imagine that after the war and great depression it felt pretty damn satisfying to think that I could have a job, a wife, two kids, a house, and put food on the table. Since then, though . . . that doesn't feel like nearly enough. We all have supercomputers in our pockets. A complete dumbass can be 100x more productive than someone in the 1950's just thanks to technology they had no part in developing. Everything feels cut-and-paste. Nothing is organic... just doing what my grandparents considered to be pretty good is not worth a damn.
So, you aspire for more. You pursue something that feels inventive or creative, like an art or running your own business. After all, we now have social media and youtube showing us people who seem to be living the "influencer life," or they are making money from their art or music . . . boy, THAT would surely fill the God-shaped hole! Two issues: (1) it probably won't, but more importantly (2) there are 8 billion people on the planet, you're probably competing with a billion, and only about 10k spots available for what you're dreaming of. You're almost certainly not going to get that pipe-dream anyway. So . . . no purpose, just depression.
A lot of people will point towards family as an alternative. MY kids will be special because they will be MINE from my super special DNA, therefore I'll get an animalistic satisfaction from raising them, right? I haven't experienced that, so I can't speak to it from personal experience, but in a world where realistically both parents - if they stick together - will have to work some to afford life, you're hardly going to do any of the actual "raising." I don't think this works as well as people claim it does. It also makes your life so very one-dimensional.
Other people get driven just to make money. They're going to succeed by climbing the corporate ladder. They work 60-80 hour weeks. They post on linked-in. They have no depth to their life. This is a purpose, but it's certainly not good, and there is no room in their life to make the world around them better.
This lack of purpose, or crappy purpose, means that in our precious free moments we fill it with distractions: whatever can keep our brain occupied as it tries to scream at us that it needs a purpose and we are starving it. Instead we watch shows or click on websites or scroll through social media and make the problem worse. Often we attach ourselves to "teams": sports teams, political teams, fictional groups in media, or taking silly sides on topics on the internet. These are all things where we have little to no control over the outcome, yet we will let our emotional reaction ride on said outcome. No purpose. No agency. It leads to being unbalanced, unmotivated, uninformed.
It means people have little impact, positive or negative, either globally or locally, and it makes people far more susceptible to being taken advantage of by scam artists. It leads to a society stuck in a ditch with no ability to dig itself out. We have a populace that avoids conflict, pain, or anything negative, because there is no positive purpose to live for, so our instinct is to therefore cut out as much negative as possible. Have you ever felt the need to stand up for a principle that didn't have much practical consequence, but you felt strongly about doing the "right thing," so you made a stand, and then you got no support - maybe even annoyance from the people around you? This is what leads to that. I imagine a lot of people here understand that, because it adds up over a lifetime. When you realize you can't make a big impact on the world alone, but no matter how much you scream at people you can't drag them away from their sportsball or netflix or political news source of choice, you start giving up. Then, nothing changes. Nothing gets better.
People say it's a society of sheep and wolves, but when you think about it it's more like vultures and a corpse.