“Utility” is not a concept I subscribe to per se, unless you just mean use-values in the same sense Marx uses them. I am responding to the concepts you are using. In a communist mode of production, production is, in the famous quote, “according to need”; in a capitalist mode of production, production is divorced from need, and we find production for the sake of production.

Well, since you still haven’t told me what you think the word means in like a formal, well-defined, academic sense, I can’t really tell what your objection to it is. Like at the end of the day it’s just a word, and i have never actually run into a situation where if I thought about it for five minutes, I wasn’t able to actually reconcile the academic concept of utility with Marxism. And in practice, thinking about utility and realizing the highly arbitrary nature under which utility is realized under capitalism, is one of the main things that drew me to leftist economics in the first place.

Marxists use the word “exploitation” differently to its colloquial use. “Exploitation”, in Marx’s critique of political economy, refers to the extraction of surplus-value. I’m not sure if you know what that means or not. I can explain it if you want but you can also look it up; it’s a pretty basic part of Marx’s critique.

I certainly am not using it in a colloquial sense and in fact, I have been using it in the Marxist one the entire time which is why I described a market economy where literally all of the firms are compulsively required to reinvest the very surplus revenue you describe back into the firm itself. So again I’m asking you: in that situation, where is the exploitation?

And then the next important thing is to simply realize that such an economy, whatever you wanna call it (because for some reason you seem like you don’t wanna call it a market and I don’t understand why, but fine) is completely consistent with what is called a “market” in neoclassical economics, and so even if for some reason you think it’s really valuable to say that an economy stop being a market when everybody in the economy isn’t trying to mindlessly get ahead anymore, you can still analyze it as a “market” and resisting this extremely useful framework is only making your own life harder

needs are either met or not

When you have hundreds of millions of people in your country, it's not as black and white as that, even just logistically speaking...

I see "maximizing" in this context (describing utility) to imply doing it as well as possible.

Though I suppose, "optimizing" would be a better word to use.