The entire reason for centralization is specialization. Certain crops can only be grown in certain parts of the world. Corn yields are high in in Iowa, and low in Idaho. Potato yields are high in Idaho, but rot in the ground in Florida. Oranges grow great in Florida, but not all all in Iowa (or Idaho!).
How are you going to locally distribute the production of those crops? You simply can't grow some of those crops in some of those regions.
If these farmers were subsistence farmers, then they would only eat potatoes in Idaho, corn in Iowa, and less corn in Florida (since man can't live on oranges alone). But in a 'centralized' system with distribution run by 'multi-national' corporations, each can trade with the other, and eat a well balanced diet of corn, potatoes, and oranges.
Waste does not cancel out the advantages of high productivity. Cereal productivity is in the 6000-9000 kg/hectare range for the US and Western Europe. Its is 2000-3000 kg/hectare for middle income countries like Turkey, Mexico, and Russia. It is 1700 in the Arab world, and 1400 in Sub-saharan africa. In Medieval England, yields would be 8-10 Bushels per Acre, which at 56 lbs to the bushel is about 600 kg/hectare.
So modern crop methods are at over a 10:1 advantage over Medieval farmers, and 5:1 over third world countries. Even if you assume 50% spoilage and waste, we still come out way on top.
Remember, one of the big reasons that crop production is so high is that crops are ONLY grown where they are optimally suited. You can grow corn in Idaho and potatoes in Idaho, but no one does because the yields are low. So instead corn is only grown in Iowa with thick black soils, and summer heat and rain, while cool-and-dry-loving potatoes grow in the semi-desert highlands of Idaho. Also, oranges are grown in Florida where freezing temperatures literally cause a state of emergency to be declared. Wusses.
Waste does not counteract the advantages of modern farming techniques or specialization by location.
Cutting Edge Techniques
...are expensive. They are useful for specific things that are perishable (like lettuce) but not so useful for things that store well and have to grown on huge areas (like cereals: wheat, rice, corn). The world is fed by these crops. 51% of world calories come from cereals. Even in the affluent United States, 25% of our calories come from cereals, and another 25% from meat/milk derived from animals feeding those cereals (and 35% from oils and fats!!!). That leaves just 15% of America's calories coming from fruits, vegetables, pulses and nuts. And even those aren't ideal for vertical farming or aquaponics or what have you; peas and beans have low yield per acre and need lots of space; tree crops like olives or oranges need lots of space to grow for years before they start to fruit, etc.
Cutting edge farming has a place in the world, but will never compete with specialized monoculture in producing the calories that humanity needs.
For further reference, here is a summary of the future of agriculture, from the Economist (possibly behind a paywall)