Buying and holding Bitcoin for the long term was already proven and tested, and as far as I can see, it is very favorable for rich people, and there are large companies and several businesses. Especially for people who want a big ROI on their capital.
On the contrary, holding Bitcoin is ideal for both the rich and those that are not there yet. Bitcoin can even be their means of escape from poverty as it has proven to be able to change the financial situation of many people including the early adopters that are very much present in the forum till date.
There are people who has the word "donator" attached to their name in the forum, some of them donated as high as 10 BTC to the forum and as at then, 10 BTC was like peanut that anyone could easily afford then. Imagine those who were able to hold that amount till date, can you call such person poor? I gave this example so you can see that Bitcoin can make someone rich, you just need to HODL and see how happy and proud it will make you become in the future.
Now if there are ordinary people who are in the middle class who save bitcoin via dca, they will also experience earnings in the end, but it won't give them much profit because they won't be able to handle that much, but they are sure that they will get profit from their holdings.
You have to adjust your mindset a great deal because you are neglecting the power of consistency. If you consistently invest $100 per month into Bitcoin via the DCA method, give yourself 10 years from today, you will be financially comfortable. An average worker will be able to make such investment depending on their country of origin and what the minimum wage is. But the crux of the matter is that investment in BItcoin can make someone rich and the DCA method, which can be applied by anyone, is one way of achieving that.