I agree with you. Bitcoin’s volatility makes it tricky to trade, but DCA as a long-term strategy seems like a more reliable approach.
Every asset is volatile in nature, not only Bitcoin, which is risky to trade. To some degree, it's even safer to trade Bitcoin than other currencies, but the profit margin in the short run is little, as is the risk of reductions in price. DCA has always been proven to be the best, but one should be calculative and know when to buy and limit doing the math, especially for those who will want to buy with every little amount.
I don't agree with all you have said especially when you are bringing trading and DCA together since we know that DCA is for long term investment and not short term. You also made mention of bitcoin not giving bigger profits as though you have forgotten that other cryptocurrencies are prone to losses which make them very risky for investment. Bitcoin is just enough and highly profitable, using the DCA method to purchase bitcoin is recommended and never for altcoins that have high propensity for failing investors.