Let's put it this way - how many biplanes do you see being made?

As I understand it, biplanes have an adverse lift/drag ratio, making them less economical to run. This is different factor than having a balance between good center of gravity yet also maintaining wing in ground effect. For example, biplanes are still used for certain air show sorties even if they aren’t the main event.

The biggest benefit that biplanes (may) have involves acrobatic flight and wing tricks.

In general one wing wonders work better (and you even say some of the later biplanes not having wings right over each other).