I think the basic premise is correct, that suffering is by far the most important determinant in where utilitarianism takes us in the long term. Adding the good has far fewer world-changing requirements and consequences than removing the bad, which might say something about the raw deal that evolution hands to all individual entities. A short sketch is here, the pertinent part reproduced below:

https://www.exratione.com/2016/06/the-hedonistic-imperative-...

Suffering is not only human, however. The natural world from which we evolved continues to be as bloody, terrible, and rife with disease as it ever was. Higher animal species are certainly just as capable of experiencing anguish and pain as are we humans, and the same is true far further down into the lower orders of life than we'd like to think is the case. We ourselves are responsible for inflicting great suffering upon animals as we harvest them for protein - an industry that is now entirely unnecessary given the technologies that exist today. We do not need to farm animals to live: the engineering of agriculture has seen to that. The future of paradise engineering could, were we so minded, start very soon with an end to the farming and harvesting of animals. That would be followed by a growing control over all wild animal populations, starting with the lesser numbers of larger species, in order to provide them with same absolute control of health and aging that will emerge in human medicine. Taken to its conclusions, this also means stepping in to remove the normal course of predator-prey relationships, as well as manage population size by controlling births in the absence of aging, disease, and predation.

Removing suffering from the animal world is a project of massive scope, as where is the line drawn? At what point is a lower species determined to be a form of biological machinery without the capacity to suffer? Ants, perhaps? Even with ants as a dividing line, consider the types of technology required, and the level of effort to distribute the net of medicine and control across every living thing in every ecosystem. Or consider for a moment the level of technological intervention required to ensure a sea full of fish that do not prey upon one another, and that are all individually maintained in good health indefinitely, able to have fulfilling lives insofar as it is possible for fish. General artificial intelligences and robust molecular manufacturing technologies, creating self-replicating machinery to live alongside and inside every living individual in a vast network of oversight and enhancement might be the least of what is required.

At some point, and especially in the control of predators, the animal world will become so very managed that we will in essence be curating a park, creating animals for the sake of creating animals, simply because they existed in the past - the conservative impulse in human nature that sees us trying to turn back any number of tides in the changing world. It seems clear that the terrible and largely hidden suffering of the animal world must be addressed, but why should we follow this path of maintaining what is? What good comes from creating limited beings for our own amusement, when that same impulse could go towards creating intelligences with a capacity equal or greater than our own? Creating animals, lesser and limited entities that will be entirely dependent on us, to be used as little more than scenery, seems a form of evil in a world in which better can be done.

Given this, my suspicion is that when it comes to the animal kingdom, the distant future of paradise engineering will have much in common with the goals of past religious movements and today's environmentalist nihilists, those who preach ethical extinction as the best way to end suffering. Animals will slowly vanish, their patterns recorded, but no longer used. If animals are needed as a part of the world in order to make the human descendants of the era feel better, then that need can be filled through simulations, unfeeling machinery that plays the role well enough for our needs. The resources presently used by that part of a living biosphere will instead be directed to other projects.