We can absolutely live without them. I have never once used a centralized exchange in my entire life, and yet I would wager that I am more involved in the bitcoin ecosystem than 99% of other bitcoin users given that I use and spend bitcoin as a currency almost daily. Yes, we might not see the same fiat denominated prices without centralized exchanges, but bitcoin itself does just fine (better, in fact) without them.
We can leave without them, those centralized exchanges are not needed before making bitcoin transaction, definitely true. But from the way you post, it is clear that you are not a trader, if you trade daily, leveraging with opening and closing position daily or weekly, you will have to depend on an exchange. Please can you offer a decentralized solution for we traders as we depend on those exchanges? But only trading funds are there, winnings are withdrawn to a noncustodial wallet.