Dca strategy is not the only strategy for accumulating bitcoin and the fact that an investor is using dca strategy does not stop him from making use of the other strategy. An investor can combine two of the strategies or all while accumulating bitcoin. He can be doing dca and still buy the dips when it occurs and also do lump buying when extra cash arises. So I believe none of the strategies are ineffective since an investor is not refrain from making use of the other strategies while using dca.
Even though the DCA strategy is not the only strategy for accumulating bitcoin, but it has been the best strategy since at first, some folks use to think that before they can invest in bitcoin they will need to buy a whole bitcoin but with the idea of the DCA strategy has made so many investors to make accumulations with some fractions of bitcoins they could buy and some of them has owned more than one bitcoin using the DCA strategy but for someone who has no idea of the DCA strategy, they might just decide to lump sum and forget about investing further which does not make much sense to me because with the DCA strategy you can have the privilege of buying bitcoin at a lesser price on like someone who did lump sum and not invest again. How about buying the DIP, an investor can wait for a DIP, and it may not surface at that material time which can lead them to buying at high prices in the end when they could have just applied the DCA strategy and can buy the DIP along while they have already made accumulations. Buying the DIP, DCA and the lump summing are all different strategies to buy and accumulate bitcoins, so it is left for an investor to choose between which they find convenient and apply them accordingly.