They're certainly enough to survive, which is why they're provided in prison. The argument wasn't that these are the only things you should ever have in life, but rather that these are the only things you need in life, and everything else is a luxury.

The punishment of prison isn't free food and shelter, it's a lack of luxuries. And people survive for decades in prison, so obviously what they're getting is, by definition, enough.

I wouldn't even consider prison to offer "shelter" since you're locked in there with violent people.

The things that make prison an undesirable place are lack of autonomy and separation from friends and family. You don’t need advertising or corporations to provide these.