Because you are now assuming this, your mind looks for reasons to find evidence for it- it's called confirmation bias.
Of course there have always been inconsiderate, selfish people in the world, it's the case all over the world. However, I dont agree that people are becoming worse - humans are humans and we all have selfish thoughts and can behave selfishly at times- every single one of us.
I'll give you some examples of things that have happened to me recently:
I was buying dog food and a couple of dog toys in a pet store a week ago. I realised I couldnt carry it all and so asked for a bag - they were 10p, I had already paid by card and I didnt have cash on me, only a card. The man behind me in the queue immediately said "dont worry love, let me pay for it, it's only 10p. I thanked him and said thats so kind of you. He then realised he didnt have 10p in cash either so he left the store, went out to his car just to get me 10p for a bag. It was only 10p but the thought was so kind and helpful.
I took aforementioned dog on a long walk this morning up the downs, every single person I passed smiled at me and said good morning and I had a lovely chat with quite a few of them. These were complete strangers. It made me feel really happy.
The other day, one of my colleagues was in a minor car prang. One of my colleagues suggested we pool together to get her some flowers and a small present to cheer her up.
Now, of course I could probably list some evidence of selfish things I have seen too but the point is- you will find what you are focusing on, its literally how your brain is wired.