Adults and I hope I don't end up like them

Assalamualaikum warahmatullahi wabarakatuh everyone, This has been weighing on my heart a lot. I've argued about it with my parents many times, and I'm starting to think most adults act the same way - and that maybe, over time, I might become like them. I'm the youngest in my family, and decisions have almost always been made for me by my parents or siblings. Now when I decide something and feel sure about it, my parents tell me to ask my brothers or sisters first. I sometimes still doubt myself because since childhood I've heard things like “I can’t do it” or “it’s too much for me” from my brother, and even now from the whole family. I feel like this attitude has become worse - in me, in my family, and in how I view people generally. A few days ago I was telling my mum to eat properly and include more protein, but she brushed it off saying it wouldn’t suit her. When I suggested she look up a protein source that might work for her, she said she would. Then she joined a new coaching group - something like Herbalife - and suddenly she started following a protein-rich diet. I told her, “just because I’m young you won’t listen,” and she didn’t respond. I've seen this many times: elders dismiss younger family members, maybe because they think they know everything and we don’t. Adults can become stubborn or closed-minded as they age, and I worry I might too. I’m trying to be aware of it and control myself. But because of everything that's happened, I struggle to trust myself. No one gives me confidence that I can handle my own choices. All I ever hear is that I can’t. So I’ve decided to speak less, since people often won’t listen even when I’m trying to help. I’ve told my mum that adults don’t listen, and she becomes upset whenever I bring it up. At the same time, I want to try to see things from an adult’s perspective so I can understand their reasoning better. I hope to learn what they value so my family can begin to trust my judgement as the youngest. If you read all of this, may Allah bless you. JazakAllahu khairan.