DCA defeats this but only with BTC.
Altcoins? Trust me, I tried this in 2017. Down 50%? I bought. Then down another 50%? I bought more.
Never went up for 99% of coins, I lost so much precious BTC doing this.
You are almost correct here but if someone took a really bad entry on bitcoin like at the 2017 tops and start dcaing from there, you would blame bitcoin too for 3 years before you get to earn some profits. As bitcoin is getting older, the PA is getting slower too. Instead of DCAing from any price level, it would be better to understand some TA and take sensible entries and exits along the way.