Yes bitcoin is a closed system hence why we can not change anything from the past transactions as displayed in the blockchain.
I wasn't expecting this from you either. Op literally doesn't know anything about how Bitcoin works and what it is. Bitcoin has never been a closed system and before any changes are made, it needs the approval of the community or developers before they are implemented. It's an open system where everyone can participate. If you are referring to its total supply of 21million then I'll agree with you because that's actually a closed supply. but not it's whole system being closed.
Do you agree with me that those who sell bitcoin are losers, and those who buy and keep bitcoin are winners?
No I don't. As an investor, you chose how and what you get to do with your coins. I don't see how selling some coins makes anyone a looser because that's how Bitcoin is circulated through networking. People have to sell for others to buy and invest as well. I guess you need to understand basic economics abit mate. When new coins are mined, miners supplies them into the market by selling. Do we now call them losers?
You should learn to quote properly. Read this thread
[TIPS] to avoid pyramid quotes (for Newbies)