What would you eat if

Are we talking about ready meals, cakes, biscuits, jars of sauces etc, or more basic things like roasted coffee beans, tea leaves, wine, dried pasta, pressed cooking oils, butchered meat etc?

If the former then there would be pretty much no difference for me (except maybe for gravy granules), Everything is cooked from scratch including cake and biscuits (I freeze portions so don't have to eat an entire cake in one sitting!). I enjoy cooking and at one time went down a rabbit hole over "ultra processed food" so stopped buying it in virtually every case.

if you mean the latter, more extreme examples, then that's very interesting. I bake my own sourdough bread, but rely on pre-milled flour and salt from a packet. I could ask my mum how to make wine, but I'd need brewer's yeast from somewhere. I've never killed and butchered my own meat, but I'd be willing to try. It would mean giving up a lot of the more exotic imports like chocolate and coffee. That would be irritating, but not impossible. 

I was thinking what would it be like if we had no ready meals and jars of sauces etc, just bread, butter, chesses and meat and cakes, like we used to when I was a small child, before we had big supermarkets and people went to the butcher, the baker, the greengrocer, the fishmonger etc, there were a few tinned goods like baked beans and peas, jars of ketchup and chutneys and jams, but not a great deal else. Most bread wasn't sliced and had to be cut, tin openers didn't have a ring pull, you had to open them with a can opener with a spike and blade that you stabbed and hacked around the tin with. Milk and other dairy products often came from the milkman, along with orange juice and maybe some fizzy drinks, if they didn't have a sperated delivery.

Delayed response (because I turn notifications off), but...

The reason I learned to cook originally was because my mum was a health conscious wanna be middle class stay-at-home 1970s/80s mum, complete with aga and Laura Ashley dresses.

There were hardly ever biscuits or cakes in the house because: sugar. So I got the Delia Smith cookery book down from the high shelf (that involved climbing on the Welsh dresser), found a recipe and began cooking. 

No idea how old I was when I started. I know I needed a chair to reach the countertop. I baked in secret as I never slept well so would be up at 4am sneaking into the kitchen and making scones or victoria sponge as quietly as possible.

Recipe books just clicked for me. Like programming the ZX Spectrum or reading music. It was a code I could learn and use. I still read recipes now, although usually adapt them to my own style 

Delayed response (because I turn notifications off), but...

The reason I learned to cook originally was because my mum was a health conscious wanna be middle class stay-at-home 1970s/80s mum, complete with aga and Laura Ashley dresses.

There were hardly ever biscuits or cakes in the house because: sugar. So I got the Delia Smith cookery book down from the high shelf (that involved climbing on the Welsh dresser), found a recipe and began cooking. 

No idea how old I was when I started. I know I needed a chair to reach the countertop. I baked in secret as I never slept well so would be up at 4am sneaking into the kitchen and making scones or victoria sponge as quietly as possible.

Recipe books just clicked for me. Like programming the ZX Spectrum or reading music. It was a code I could learn and use. I still read recipes now, although usually adapt them to my own style