There’s a couple parallel issues going on with food availability, but I really see three primary ones.
The first is the timescale. The default timescale of 14 days per season means that for every apparent day, almost a week goes by in ‘real time’. So if you kill a deer and fill a large waterskin with water, that will last you a month or so (at least). If you bump the timescale up to 91 days/season, canned goods become a luxury until you’ve enough killdozer to drive off into the sunset. And like others have mentioned, the setting means there’s going to be a lot of canned goods.
The second is the ease of scavenging, in terms of effort, risk, and reward. The difference between low and high survival on scavenging is minimal in terms of rewards, the only thing you invest is a trivial amount of time, there’s zero risk except with blindly eating mushrooms, and even when you just get ‘garbage’ your reward can be pretty valuable items like glass jars or gallon jugs.
The third is that there is absolutely no reason not to pick an easily made single foodstuff as a ‘staple’ and just make that forever. As mentioned, morale is a non-factor, so the only things to think about are ‘is it easily made’ and ‘will I have to worry about catching diseases’. Biscuits are tasty and filling and probably deserve at least close to their current stats, but eating nothing but biscuits for months at a time would cause all kinds of health and psychological issues.
I’ve been thinking of how these could be addressed, but I’ll have to kick the ideas around in my head for a bit.
The current system is far from realistic, and the proposed systems are also far from realistic. Details should be added when appropriate, but it’s important to remember that the simulation serves the game and not the other way around. That’s why there’s just ‘chunk of meat’ rather than various cuts and ribs and all the other giblets when you butcher - it doesn’t add anything to the game to simulate all that.