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.
Cooks have absolutely no say in what they cook or really how they cook it.
It's Sysco food.
Your actual gripe is with local governments, the USDA and voters who consider funding any social program to be communism.