If you are going to invest in Lump Sum manner then price is very important at which you are investing your whole money. Like as I already said, investing 20k$ when price of Bitcoin is 67k$ will lock your investment for indefinite period of time while investing same amount when price of Bitcoin is 20k$ is better option. You are right in saying that we don't know exactly when its bottom or just the start of dip. So one has to do that risk analysis if he is trying to invest in Lump sum manner.
While in case of DCA there is less risk involved compared to Lump sum. In DCA, all you need is to accumulate Bitcoin slowly and based on historic data DCA for 4 to 5 years has been a profitable strategy.