"Some people mature, most just get older." - me
I think so too. I think anyone who reads The Sun isn't really mature for starters. But even then, maturity is relative. I don’t read The Sun - but I consider myself 80% mature, even being mid-20. Women are definitely a lot more mature than men emotionally. No wonder marketing companies are just full of women these days from my experience - no coincidence.
I think most people can reach a decent level of maturity. But it takes a lot of mind training, thinking, reading and active practice. For some lucky people, being high EQ is natural. For others, it requires a lot of active thinking.
I think internet forums really do reveal the maturity distributions with people over 20, since such characteristics wouldn't be found in the media with the exception of showbiz/music artists perhaps!
Just some thoughts.