Pleasure or fulfillment

I am attracted to the concept of utilitarian ethics and maximizing the good for all of society- however I am not convinced that the good we should seek is necessarily pleasure and the absence of pain. I think that a better suited term would be fulfillment instead of pleasure or happiness. I am not sure that Mill would disagree with that, he makes the distinction between lower and higher pleasures, “It is better to be a human being dissatisfied than pig satisfied; better to be Socrates dissatisfied than a fool satisfied.” (15). I believe that he is speaking more to fulfillment, specifically fulfillment of the mind to be synonymous to pleasure. Educational fulfillment can often be far from pleasurable (grueling all-nighters, nightmares about the biodiversity crisis, etc.) but this is still acceptable under Mill’s Utilitarianism. If I learn about the biodiversity crises, have many painful feelings in reaction to it, those pains are what can motivate me to go out and try to save species, which is consistent with maximizing total good, but not necessarily happiness. If instead the code of ethics should be revolved around maximizing fulfillment rather than happiness, I am still not convinced. Mill speaks of “civilized” countries, are those countries with education as Western conceive of it; what does “civilized” mean? If morality is centralized around mental fulfillment (higher pleasures), do more primitive peoples somehow have less morality? I find this a difficult concept to accept as a measure of how we ought to act, if it is so exclusionary.