Fruit and veg without plastic is available at your local supermarket.
It can be a bit annoying to weigh it - you can use reusable bags for that - an easy one would be that you can get at least 10 uses out of the clear plastic bags you take the stuff home in for example.
Processed stuff is harder sure. I tend to not really eat that stuff, staples are cheaper anyway.
I agree that most people don't do this - well over half of the supermarket is full of items I'd never even consider buying - but that doesn't change the fact they could.
I actually think there's a hump in the middle of the distribution.
Essential basic foods are cheap and generally come loose (or at least you'll get 15kg of rice in one big bag).
There are some exceptions like frozen vegetables.
Processed middle of budget stuff like pre made sauces, ready meals, pre packaged small cuts of meat etc - yeah that's full of packaging.
Then you have the signalling products whereby basically you're paying silly money for ready meals in cardboard boxes or whatever.