But it can still scan a barcode and save the output somewhere. It does not "need" the plugins. If you install the plugins, however, they will do nothing without mbarcode.

I think the problem is that we are trying to use a tool (package dependencies) for something it was not primarily intended for (simplifying add-on installation), which would be fine if it did not require reversing its original meaning completely, something colloquially termed "a hack"

[EDIT] you can always have mbarcode proper tell the user to install the addons, perhaps by providing a button that goes straight to the App manager to install mbarcode-plugins if none exist.