I always thought it was a travesty that the "chefs" at my schools were just heating up junk food. It's the perfect place to achieve the economies of scale to produce whole-foods-based meals. But yet no 'real' food - dishes made from raw meat and raw vegetables that are processed in-house - was ever produced. I honestly don't think this will change in my lifetime. It's too much work and it feels like working hard, especially in a government position, is seen as making you a chump in our culture today.
I work at Google. We have cafeterias with real food. There are videos on youtube fawning over how cafeteria staff are able to tackle this logistical challenge of serving high quality food to so many people each day. "Wow you have such amazing food there" is a selling point. People take their friends to have a meal at work to show off.
This responsibility is roughly identical to the responsibility that cafeteria staff have. Feeding meals to hundreds of kids is not any different from feeding meals to hundreds of adults. Yet cafeteria staff are, like you say, treated as garbage and uncreative jobs. So of course nobody who is passionate about food production decides to work in a school cafeteria.
Money solves this (plus society giving a shit about the flourishing of children). That's the long and short of the story. Decide that school lunch is not just about meeting minimum nutritional standards and make it about the joy of serving and eating food. Vastly increase pay for cafeteria staff, increase their autonomy to produce meals, and increase their budget for ingredients.
Everything else is putting lipstick on a pig. Further constraints on acceptable ingredients or macro and micro nutritional breakdowns will just force the cost optimization to some other unwanted state.
Instead of blaming the low nutritional value of school lunches on line workers being unwilling to "work hard" because of "modern culture," consider the possibility that they aren't the ones responsible for setting the menus or budgeting the ingredients.
Your actual gripe is with local governments, the USDA and voters who consider funding any social program to be communism.
I think you are letting your biases influence your reading comprehension. I don't blame the line workers. It's not their fault. My gripe IS with the local government. Those are the the ones who have the responsibility to change the system and who seem happy to just buy Sysco. They are government workers too...