Love them or hate them there are a lot of common tropes across the science fiction genre. What are some of your favorite and least favorite tropes?
I think it goes without saying that one of the least favorite tropes is Deux ex Machina. I couldn't quite put my finger on it at first, but after watching the German TV show "Dark" I was utterly dissatisfied with it. The entire series up until the very last episode is about this inescapable time loop and alternative universes which is pretty cool while watching it, but then you get closer and closer to the end wondering how they are going to solve this impossible problem. Then surprise they just do it instantly in the last episode.
Another trope I am not very fond of is nanotechnology where there are trillions of tiny robots that can effectively act as magic. It just feels like a lazy way to write science fiction because you really want a fantasy.
A trope I do actually like despite how overdone it is, is the idea of a precursor or forerunner. It often brings to light the absolutely massive scale of the universe which I find fun to think about.
The Culture does this best. Most Culture citizens live on orbital rings. You're allowed to move to a planet if you want, but it's not the norm and the Culture considers civilisations which rely on planets to be immature. They view it the same way as dependence on fossil fuels, it's destructive and unsustainable.
Oddly enough, an example from Star Wars of all places also pops to mind. The Ithorians had a culture that included deep reverence for the forests of their homeworld Ithor, and had a very communal society, so when they got technological they built huge "Herdships" that were basically flying cities. Initially they just hovered in the sky over their planet so as to not disturb the forests on the surface, but they eventually became spaceborne and became self-sufficient arks travelling the galaxy.
They still regularly returned to their homeworld, though. Until the Yuuzhan Vong destroyed it. The Herdships were unaffected, though and basically became nomads.
I recall a thread over on Reddit where I speculated at length about what the Star Wars galaxy would be like in the aftermath of the Rise of Skywalker and the fact that the tech now exists to build Star-Destroyer-sized planet-killer weapons and it apparently is pretty cheap to do so made me think that the galaxy might be forced to go post-planetary. A planet is basically indefensible but something like an Ithorian Herdship can just jump to hyperspace the moment a Xyston-class ship shows up in the neighborhood. It's hard to speculate with much confidence given the shoddy worldbuilding, though. Hyperspace tracking is apparently quite easy now too, so if someone really has it in for a particular Herdship it might still be screwed.