This can be possible if you have money when Bitcoin is low, you have a point but we don't know when Bitcoin will low and when it's low if you don't have money to buy, just let go as it's not good to loan money because you want to buy Bitcoin at low price.
It's also tells that you must have money to buy Bitcoin if you want to invest. When bitcoin is high you have to save money and wait for it to low then you buy, Bitcoin can high any moment and low any moment that's what makes it risky, so have in mind to lose and not to gain.
You don't need to have thousands of dollars before you can start bitcoin investment, that's why we have the DCA. Good a thing that bitcoin can be bought at any fraction, depending on the money available. Yes you are right about nobody knows when the price of bitcoin will be low. But that's why it's always advisable to make plans ahead of time, by keeping a certain percentage of your investment funds for buying the dip, should in case the dip happens, so you won't be caught off guard. When bitcoin is high we don't save money and wait for it to low before buying, we buy through DCA when you think that bitcoin price is high. This is why we have the DCA. Nobody knows when it will low. Saving the money is not advisable as you might miss out buying. When it's low buy the dip, when it's high buy with DCA.