Those things you said sound evil but they're really not. Finding hyper-palatable food is just another word for finding stuff people want to eat if you're making food, something that's tasty.
Spending billions on marketing? Marketing is how you connect to what customers want. I'm a professional marketer, right and it's really really hard. If I was trying to sell food, I'd try different positioning statements, different ways to see what actually appeals to people. Marketing is not magic; it's market discovery.
And yeah it's bad whenever any company captures regulatory power. That's bad and I agree.
Optimizing for food that costs the least in ingredients, at the same time is provenly unhealthy, and has addictive properties, is a totally valid strategy for a free market but it's far from "feeding the world".
And better accessibility of unhealthy food in comparison to healthy food is a reality for many people, especially when they cannot outsource the act of buying and preparing food to others, including family, or spend arbitrary amounts of money on luxury "health food".
I'm not saying it's impossible to buy healthy food, or the responsibility of regulation to dictate what people eat.
But what you say about marketing seems besides the point to me.
Optimizing marketing of food for profit is not equal to "feeding the world".