I thought about attribute boosting foods, and special dishes that are good for ailments, more heat and cold insulation, etc.
For what it's worth, I don't think that would be a great idea (along with food that heals faster)...
-By having food do what medicine, or insulation etc should, you will only succeed at making food more valuable at the cost of making everything else less valuable... which is even worse imo.
-With attribute-boosting foods you will only lead players towards mmo-ish behaviors, with them treating food as "buff potions", eating certain foods to learn a perk, mine, fight zombies etc.
I guess it would solve one thing - I would not need to organize my food box anymore....
Yes, you wouldn't have to organize your surplus because you wouldn't have a surplus.
The question is no if the system is more complex or adds something to do but what behaviors would it change and, tbh, if food spoiled I would do almost nothing different. I already have a farm that is capable of producing enough veg stews to last until the next harvest cycle. The only real difference is I would harvest more often rather than cooking my food in larger batches.
"Why do we even have hunger/thirst in the game? What behaviors does it change? The only real difference is having to click on an item every few minutes" -
an item that, by the way, you can't run out of. That's what it all boils down to if you don't have some proper item economy.
Yes, pretty much everyone has a farm that "suffices" - if they bother making one that is. Whether or not people ignore all other sources of food (traders, loot, animals) the farm always creates a surplus and people "don't farm as much" which most usually means "don't farm at all" if their surplus is large enough simply because there is no reason for them to do it.
So yes, given that there time is a resource (especially under certain settings), I'd consider it a pretty important change. For example in a random occasion
the "let's go grind some zombies" would become "let's go grind some zombies - oh wait do we have the proper resources to make food so that we don't starve while we do it"? I'd consider this "a win".
And if we want a proper item economy and farming to become something more than farmville farming, involving some actual player decision making, a resource cost (like fertilizer) for the plant to grow needs to come back to the game.