Food takes energy to produce, transport and store, that releases (much) more CO2 for now than plastic packaging. Plastic is rather efficient, you only need a tiny drop of oil to create a lot of packaging.

If food production at some point becomes CO2 neutral you still have a lot of other detrimental effects to the environment from food production to account for. Plastic is a net positive for the environment when it comes to food packaging.

But if you need to ship twice as much unpackaged as packaged you're harming the environment in other ways.