You're right. It is not only time and it is not only bad experience. I have been trading since 1997 but I start to be consistently make profit last one year and I have friends who started to trading in high school, he is mid 40's now and he is still terrible trader. My brother is trading last 15 years and still he is losing money and every time he lost badly. His motto is 'all or nothing' so many bad experience.
You would ask; if you are good at trading and they are bad why you didn't help them? Answer of this question is also answer of your question. I did; I recommend to them books after they ignore me and still they were losing I bought the book (remittances of a stock operator) and send them as gift. My bother has never read it. My friend read it and ignore it. Recently my friend start to write to me on whatsapp. I put him such a situation that he can not ignore his mistakes but result wasn't became better on trading, result was escape from me. We were close to break 30 years friendship. I understand that, for him it is not about trading it was another something. As Ed Seykota said 'everybody find what they are looking in market'
So what it makes you experienced trader in my opinion is being open mind, critical mind and self aware person. You have to be honest to yourself. You have to search for true not what is in your mind as true but real true. You have to have passion not addiction of gambling. If your character is not improve itselves that way you would always be like a child in front of markets. This is nothing to do with time. What about bad experience, it is not about experience but how you deal with that experience. If you blame broker, your wife your children, your computer or birds on air than you will never get something from that bad experience next time when it is repeat.