The economics are so familiar that nobody actually gives them much thought, anymore than people give serious thought to explaining what food is, why bathrooms are necessary, and how those two things are linked. Explaining money, resources and scarcity is no more necessary than going into gravity or breathing.
But if all a space opera does is translate modern problems into a setting with spaceships and rayguns, is there really any point? A Song of Ice and Fire could be translated to a space opera easily enough. Star Wars could be recast as a fantasy. The choice of setting is little more than aesthetic. But sometimes there's a compelling reason to pick a genre. Lord of the Rings would feel different if the magic was just sufficiently advanced technology. Frankenstein's monster could have been a homunculus or golem but those would have been monsters of the occult, old and familiar. The Creature must be a product of modern science, a magic not stolen from the gods but of man's own devising. Gepetto making Pinocchio out of wood relegates it to fairy tale but Noonian Soong making Data out of a positronic brain and blinky doodads makes it science fiction, somehow more plausible.
I'd like to have conflicts that remain believable but require a scifi setting. Star-crossed lovers? That could be in Verona or LA. Two brothers struggling for control of the family business? That could be Memphis, either Egypt or Tennessee. But the lovers might not be of different classes or races but different species. A freeborn prince of the financial empire falls for a genetically-engineered pleasure slave? Different. The brothers are actually a series younger clones and their "father" pits them against one another to see who is the worthy successor? A little more interesting.
So, what are the conflicts?
PracticalIt comes down to something that makes sense. Nobody has to take a lot of time explaining it.
Economic. You want a new market to sell your products to, access to raw materials, or transit through a region to get there. Someone stands in your way. Or you don't feel you're getting a fair shake and you can't settle your differences in the marketplace.
Territorial. They have land you want. Access to markets isn't enough, you want it all.
Practical Politics. Who is in charge, who calls the shots? I subscribe to von Clausewitz's suggestion that war is politics by other means. "To jaw-jaw is always better than to war-war," as Churchill said, but sometimes the only way to get what you want is to take it. This could lead to war between polities or civil strife within a polity. Power struggles often turn ugly.
DoctrinalThis is not going to be a necessary conflict, though the people involved may feel differently.
Religious. Something about what the other guy believes is so repellent they must be disabused of it by any means necessary. Could be an understandable moral failing like slavery or something silly like sexual practices.
Philosophical. Presented as more reasonable than a religious belief. Slavery can be presented as evil in light of reason but the same righteous reason can be applied to a conflict over eating toast butter-side-up or butter-side-down, something that is ultimately quite silly. And while one person argues capitalism vs. communism has the same weight as slavery, another will argue it's buttered toast. I would also call this impractical politics.
The practical stuff is all familiar. Hitler wanted another country for lebensraum, Space Hitler wants a planet. Same difference. Imperial Japan wanted access to oil and raw materials, Space Japan wants access to antimatter and magnetic monopoles. The United States sends Nixon to China to normalize relations and open markets, Space America sends Bat Durston to the Empire of Space Amazons. It's all familiar. Maybe Space Germany is flooding the market with cheap automation machinery that ruins the value of labor on your planet. That last one is called the luddite fallacy by economists who insist new jobs will always open up for the displaced. We're entering an era of structural unemployment where there simply aren't enough jobs and entire classes of people will be shut out of the economy. It's actually going to be a very immediate problem and not something for the realm of scifi.
I think that Doctrinal disputes will be the avenue for the most esoterically scifi of conflicts. We can see culture shocks and conflicts where ideas are seen as poisonous. What happens if biological immortality is discovered? What if brain backups and clones allow multiple copies of the same personality operating in a society? What happens if a post-scarcity society exists in the same geopolitical space as a scarcity society? We flip out over polygamy, homosexuality, incest, certain sex acts, cannibalism, etc. Blasphemy and apostasy are hot buttons for other contemporary cultures.
Could transhumanism cause the same level of disgust as transexualism does today? First and Last Men brought up the idea of creating successors to our own humanity and Brave New World had not just ubermenschen but untermenschen created to serve society. While it may be worrisome to imagine designing a superman, it feels as repugnant as foot-binding to cripple a human mind to make for a better service animal. Dune gave us a jihad against thinking machines. When what it means to be human becomes fluid and open to debate, some might decide to say "NO! It's not up for debate!" and tell us what the answer is. This sort of thing was postulated in the Night's Dawn Trilogy where those who embraced advanced biotechnology along with consciousness and memory transfer came to be known as Edenists and those who rejected it were Adamists.
There's thinking that certain scifi technologies could be considered too dangerous such as causality-violation weapons, certain kinds of nanotech and bio-chem weapons. David Langford created the concept of an image that could hard-crash a human mind just by looking at it, something he called a basilisk. Other ideas that have been floated are perfected brainwashing techniques that could be every bit as effective as love potions from fairy tales. Simulation as Lotus Eater Machine and virtual reality = the ultimate drug have come up before. Red Dwarf's take on the fatally addictive game Better Than Life is a personal favorite. It's easy to imagine a Women's Christian Temperance Union going after VR saloons.
So, this is not new, the idea of things that are taboo because they are too inherently dangerous, morally corrosive, or distasteful to be tolerated. But this is the future. Can we think of really good new ones? Or bring up old ones that have been forgotten?