If there are only bull, then how if no one want to buy in peak, maybe in my mind it is like ponzi which at the end no one buy and then who buy in peak will lose. I think everything in this world need to be balanced. Although bear market come, we still can gain profit with future trading.
Ponzi makes one centralized organization earn while they pay with others money, this is trading market, people earn, people lose, it all goes up and down, veeeeery different things. By your logic stock market is a whole ponzi that nations allow, it is not. People who bought at 20k in 2017 and sold later on when it dropped under 10k lost more than half of their money, that was bad right? They would have called it a ponzi as well.
However the ones that kept it and sold after 60k made 3x in 3 years, would they call it a ponzi as well? I do not think so. So do not be worried about ups and downs, that is going to happen and occasionally you are going to buy at the top but that doesn't mean that the top will never be reached again, I do not know when and I do not know how but one day we are going to be above 64k once again and break the ATH, that will surely happen, we just don't know when.