Yes I agree with you, using the DCA strategy does not hinder an investor whether the price increases or decreases. However, using DCA has many benefits such as
- reducing risk
- reducing the average purchase price
also market timing is not required and it is possible to invest steadily, the DCA strategy is a strategy that will help you survive in investment
Many people in the world are now rich by investing through the DCA strategy and they are investing regularly without any hesitation.

If you are wondering how to start DCA then it is very easy for you,
you just have to buy Bitcoin with the money left over after all your expenses, weekly or monthly through the DCA strategy. I see the DCA strategy as an easy and effective way to invest in Bitcoin. And yes it encourages new investors
I actually like and agree with you on DCA being one of the simplest and most effective ways to stack Bitcoin.
But that part where you talked about using all the leftover money after expenses to buy bitcoin. I wont fully agree with that, because realistically, it is not even practical in real life.
Even after handling the major stuff like rent, bills, feeding and all, that leftover (discretionary income) still has a small role to play. Life is not just Bitcoin

there are always small small things that comes up. Like maybe tipping your kids if you have kids, buying them little gifts, help someone, or even just take care of random little things.
So you saying someone should put everything into Bitcoin, what then happen with those little things? You could most likely go back and start touching your investment.
It is more realistic to just use a portion of that leftover(discretionary) money instead.