I really hate this 'muh generation' stuff and I really don't like to take part of these debates, but I feel like I have to write this. It's always been the same. There will always be people who are more mature than others in every generation. Some people never mature mentally or take a long time to mature, whereas some are very mature and down to earth even at the age of 12. (uncommon but I have seen this happen)
In favour of the other side of this debate, though, as someone who is born in 2001, I can say that I have been exposed to loads of dumb crap and trends and I can see how these would make people more immature by kinda lowering the standards. I don't have to give any examples, just log on to any form of social media. This still does not change your personality, though.