A few things I've noticed about space opera tropes and conventions, collected over too many late nights with used paperbacks and a reading light that keeps dying:
Every galactic empire in fiction falls. Every single one. Writers keep building them just so they can tear them down. And readers keep showing up for the collapse because we've all watched something we thought was permanent dissolve in real time. A job. A relationship. A country's certainty about itself. Space opera tropes work because collapse is the one human experience that scales to any size.
The "chosen one" trope gets mocked constantly, but it keeps selling. I think that's because readers don't actually want to believe they're special. They want to believe that being put in an impossible situation could make them rise. There's a difference. One is ego. The other is hope.
Becky Chambers wrote The Long Way to a Small, Angry Planet about a tunneling crew where the "plot" is really just people learning to live with each other in a cramped ship. No war. No galactic threat. The stakes are entirely interpersonal. It sold like crazy and it baffled people who thought space opera conventions required fleet battles and body counts. Turns out readers were starving for tenderness at that scale.
Most space opera tropes are Westerns with the serial numbers filed off. The frontier. The lawless territory. The lone figure who can operate outside the system. Swap the horse for a starship and the saloon for a cantina and you're basically there. Writers who realize this early tend to write better space opera because they stop trying to invent and start trying to translate.
Lois McMaster Bujold gave Miles Vorkosigan brittle bones, one of the most important family names on the planet, and more charisma than any room could hold. He's the opposite of what his militaristic planet values. And the whole Vorkosigan Saga runs on that friction, the gap between who he is and who his world says he should be. Four Hugo Awards came out of that tension. Which tells you something about what readers actually want from a protagonist. Incongruence. The feeling that someone doesn't fit their world and is fighting it anyway.
The AI companion is the most interesting space opera trope right now and I'm not sure anyone's gotten it completely right yet. Megan E. O'Keefe came close in Velocity Weapon with a ship AI that might be lying to its only passenger. The whole book hinges on whether you can trust the voice in the room. That question used to feel like science fiction. It doesn't anymore.
Space opera conventions almost always include a scene where a character looks out a viewport at something so large it breaks their sense of self. A nebula. A ringworld. A fleet stretching past the horizon. Writers include these moments because awe is one of the few emotions that genuinely can't be faked on the page. You either feel it or you don't. And if the writer doesn't feel it first, the reader won't either.
Bujold once wrote: "The dead cannot cry out for justice. It is a duty of the living to do so for them." That line does more worldbuilding than ten pages of political exposition. One sentence, and you understand an entire character's moral architecture. That's what the best space opera tropes are built on. Conviction first, technology second, and the reader can always tell which one the writer cared about more.
I keep going back and forth on whether faster-than-light travel is a crutch or a gift. It handwaves the biggest logistical problem in the genre, which feels lazy, but it also frees the writer to focus on what actually matters, which is people making decisions under pressure. I genuinely don't know where I land on that. Maybe both things are true at once.
Peter F. Hamilton's Commonwealth Saga has dozens of POV characters spread across centuries and multiple star systems. It should be unreadable. It's not. Hamilton proves that if you can keep the reader oriented, there's no ceiling on complexity. The trick is that every subplot, no matter how distant, eventually pulls gravity from the same center.