The flavor has to be more intense before it freezes as the cold numbs your tongue. It looks like you made more of a purist chocolate recipe with a strong chocolate flavor, not too sweet. Note that many commercial chocolate ice creams are sweet but not deeply chocolatey (chocolate isn't actually sweet).
Note that chocolate itself (rather than cocoa powder) can be hard to deal with because of the fat content. Also, adding more sugar is fine, but can make it harder for the ice cream to freeze (same with alcohol).
Last, you can't buy today and churn tonight unless you buy an expensive one with a freezer. For most, you have to put the bowl in your freezer the night before.