The topic has become a debate of buy the DIP vs. DCA, but it won't truly matter what you "must do". You just do what you want to do or what you're comfortable doing. Plus how you buy will never be as important as what you do after it, which is HODL. If you can't HODL and have a low time preference for Bitcoin, then you have already failed.
Ask yourself, why are central bankers offended by the existence of Bitcoin like it's a declaration of war against them? I honestly don't know why, but if they really hate it and discourage people from owning it, then it's probably doing something right.
At the end, this boils down to what one is comfortable with and this makes the argument not a big deal. But truth be told, the comparison and arguments has enable many people to see beyond what they knew before by using points raised by others and their experiences to compare the advantages and disadvantages of the various methods.
When I learnt about the DCA method, I fell in love with it and started applying it until I realised I have not gotten the quantity of Bitcoin I planned getting before the end of this year. The DCA method may help but I feel as we move towards the end of the year, prices might begin to rice and this will reduce the quantity of Bitcoin I could get. By asking myself what will be the essence of holding the money when I could just put it in when I see a decent price. So I made some adjustment which is buying more using instant buy while still maintaining my DCA amount even up to this moment. This change of style was inspired by a discussion here where some people confirm that be combining the DCA method and buying the dip. So I tried it and it worked for me.