@DitaBear hi there. I relate to this, for a lot of reasons. people all the time tell me how mature I am. I'm 17, and I get told all the time im an old soul and I'm "almost too mature" for my age. but at home my parents never let go about how immature I appear to be, and how, like you, they say I haven't developed as a person and all this hud that I really cant stand. most of the time I agree, that I am an old soul, but when I listen to my parents and think that I'm not mature enough and blah blah blah, I notice how much it tears me down.
point of all that was, is sometimes you just have to let go of what people say. I of all people know how hard it is to let go of what family members say. my dad says a lot of awful things about me that usually aren't true, and I just have to let it go.
keep in mind your family have been the ones to see you make your mistakes in life. that is why our family members views on us can sometimes be flawed. they see you at your most vulnerable and much of the time miss-understand us. this is why family members, who are mostly older than us, typically have a sort of distorted view on us. I recommend actually going to a friend or something and genuinely ask them how they think your maturity is. and if its bad? its just something to improve. I know that as human beings we all the time have lots of flaws that we hope to change and are working on changing. the pile sure is high. but I think one thing that you could change as well is not only your maturity if you are more on the immature side, but also work on letting go of the past, and letting go of hurtful words.
don't beat yourself up just because you cant change overnight. your only human, so please please please remember this. above all else don't give in. exert some self discipline and just keep pushing yourself! its okay to fail. remember this too. failing 10,000 times is 10 x better than never trying at all. there is no better teacher than failure. failure is your friend. :) love yourself, and learn to let go of the hurtful things in your life. you've got this!