In countries that produce their own food, and export (e.g. the United States), there will be NO shortages other than local ones caused by supply chain disruptions (which appear to be caused by dumb government policies and labor shortages), though prices will probably rise since demand elsewhere raises prices everywhere (e.g you may be offering $10 for a quantity of wheat, but someone around the world will be offering $25 for the quantity, and if transportation only costs $5, guess who the American farmer will sell to). For American farmers, this will probably be a happy time.
In countries that do not produce there own food and rely on imports, there will be serious inflation and possible shortages. In Ukraine, there will probably be severe inflation and shortages.
The economy is hardly in ruins. In many countries there will be steadily rising wages (in part due to falling labor supply, largely caused by low fertility for the last few generations), and a increased demand for many goods and services (e.g. tanks, fighter planes, ammunition, coffins, etc.).
Of course, if the powers that be decide to nuke the world, that will have a serious impact on the economy and food supply (though it will probably mitigate the problem of global warming since soot in the air blocks sunlight – the world wars created bad winters, but a nuclear war could cause multiple years of “no summer”). This is probably an unlikely scenario (as we can all rely on the integrity of good judgment of Mr. Putin and and Mr. Biden, right???).