Yes, your investment knowledge is profound. Investment is a commitment, not a transaction. The confidence that your capital will expand and your investment will pay off. Your supermarket comparison of understanding accounting and expecting free things is undisputed. Investment requires money, otherwise knowledge is meaningless rhetoric.
Regarding Bitcoin, your point is solid. Waiting for complete knowledge before acting hinders success. Bitcoin's value fluctuates, and no book can prepare you for its emotional impact. Certain human traits only appear when money is at risk. Experience is the key here. True education comes from holding, seeing the price fluctuate, and spending sleepless nights wondering if you made the proper option. Replicating it is impossible. As you said, understanding Bitcoin involves starting small, following the DCA technique, and learning on the go.
The initial definition of the strategy simplifies many aspects that will concern your investments. If you initially know that you are buying Bitcoin for the long term and will hold it no matter what happens, this makes your plan clear. Next, you just have to determine when you will start buying and how you will do it, and price when you will stop buy.
It seems to me that a clear understanding at the very beginning is already half the battle, then everything will depend on the investor’s discipline. Knowledge is also important, because before you start investing, you must thoroughly study the asset in which you are going to invest money, a strategy without knowledge will not work.