Games like Mass Effect and Knights of the Old Republic are fantastic games. I've replayed most of them a few times. Each time I do, I get drawn to something that's not quite in the games, something I can almost taste.
Not sensawunda or nostalgia, but a whole missing genre.
Let's design a Mass-Effect-style game with Star-Trek-like ideals.
Old Star Trek was about being a mature civilization in a universe full of amazing marvels. Basically the opposite of a coming-of-age story, Star Trek was about adults finding the universe contains unending wonders. This is not the theme of any RPG I know of, but it could be. We have the power.
First let's focus on "wonders". To be honest, we already create wonders for the player in these kinds of games. We just don't play them up enough to have it register.
An example of this is Mass Effect. In this series you'll visit dozens of different hostile environments, hundreds of different classes of ships and space stations and planetary settlements. You'll see caves, plant monsters, psychics, ancient alien hive-minds driven mad by abuse, creatures so old they eat a galaxy of life forms in one bite, artificial intelligences struggling to work out how and if they should live, and so many more things.
Most of these sci fi RPGs and many horror games use the close-third-person camera. This tool is so powerful that I don't even think they know why they chose it. They chose it just because it always worked before... but there's a reason it's evolved to be such a core part of these games. It's the most powerful camera for showing us wonders and immersing us in amazing places.
1) We can see our window character. Both how they look in comparison to the area, and how they interact with the area/are interacted with by the area. Because we can see how our avatar compares, we know how to feel about the area.
2) We are still zoomed in pretty close. This allows us to make out all the details, as well as get a real sense of scale. When your camera zooms out too far, it's hard to feel like you're inside this wondrous place, and you can't make out any details of how other people feel about being there.
3) We can use standard cinematic techniques to draw focus and change mood. Slow pans, zooms, depth-of-field, shaking, tilt, and many more cinematic conventions can be flat-out stolen, and they'll work fine. Moreover, the camera is flexible enough that it can become first-person or bird's-eye as needed, giving us the best of all worlds.
By understanding the advantages the close-third-person camera gets us, we can play those up to create a more powerful and distinct sense of place, scale, and wonder.
For example, if we land on a world full of toxic electrical mists, our main character wears a heavy suit. We know it's a toxic environment because we can see our character plonking around in this heavy suit. Even the dialog has a tinny radio sound, and we can hear the KKkzzsshshhhh of sand blasting against our visor. We can punch it up by making the sound vary depending on the direction you turn, since the wind is blasting in one direction. When the electrical mist gets bad, we can see the flickering purple sparks on the skin of our suit, hear the radio break into static. We can even adjust the camera to a lower, hunched-down angle when the wind picks up.
Virtually every "amazing new thing" can be done using similar methods. If we discover a new species, how our avatar physically interacts with them will tell us how to feel about them. We can see how the locals react to us as we wander around in various costumes and deal with places built for creatures of alien proportions. If we find an ancient, damaged space station, we'll watch our avatar duck and crawl through shattered hallways, float across zero grav areas.
This is more work than just using the same walking animation all the time and simply making each level with new arrangements of the same meshes, but I feel like it's worth the price. A lot of the techniques can also be re-used - for example, the wind-blast sound pattern can be reused in the vents of a space station, or during a hull breach, or in a dock when a ship fires retro-thrusters, or even in a humorous way when your admiral is chewing you out for blowing something up.
Basically: if we radically increase the immersion of each new place, we can make each new place feel more amazing and new.
Those optimizations need to be backed up with some serious changes to how the game lets us interact with the location/have our interactions moderated by the location. This is where the "adults" half of "adults discovering wonders" comes into play.
We can argue over what being mature means, but for the sake of this design, let's say it means appreciating peace and life, and accepting that nothing is perfect. That is at the heart of a lot of my favorite Star Trek episodes, so that's what I'll be using as my measuring stick here.
That doesn't mean having a pacifist game. It might be possible to make one, but for now let's assume the game is still largely like Mass Effect or Knights of the Old Republic: you are fundamentally gonna get in a lot of fights.
How can we make maturity part of the game, despite that?
It's about allowing the player to appreciate the complexities of the places and situations they are in, and taking actions which take place within that complexity rather than just cutting everything apart.
1) Show people living in these places, show their joys and hardships, let them do things besides just sit around and repeat one line. It doesn't have to fit into a large algorithm or anything, it can be pretty basic, but focus on their concerns and their joys. Nearly all dialog, subquests, and exposition can be made part of some NPC's life, so obviously do that.
2) Show that things falling apart is bad. As lumpy as local society might be, anarchy would be worse. Ideally, show it in reaction to the player's choices: if the player takes too heavy a hand, chaos forms in the vacuum they leave. Many of the player's missions might be to try and help in places where this has already happened, which will keep it from being too blunt.
3) Party members. Have several party members along, or even have them comment over the radio. If each party member embodies one particular theme of the game (as is pretty common), they can comment on the things they see and the player will be able to easily understand the context of the comment. Of course, they can also drag the player into the local mess.
4) Recurring NPCs. Other mobile NPCs can visit many places and can bring their own nuanced chaos into the mix. Working with or around these NPCs and their factions can add a solid foundation to build on for the player's own nuanced interactions.
5) Refining choices. This one's a bit complex.
Basically, the first time you encounter a choice, you don't have much complexity to your response. But you keep revisiting the situation, and each time your options get more refined.
For example, a seedy space station has a problem as to whether it's being run by the locals or by the barely-inhabited planet below. When you first arrive, you can choose to side on one side or the other, or neither. You'll learn more as the situation unfolds, and your choices get more nuanced: you can try to put pressure on one side or the other to implement reforms or switch people of power in and out. You can gather intelligence and make surgical strikes or robust defenses. You can choose who gets a captured warship... even who gets to pilot it.
Writing these kinds of nuanced trees can be a little daunting, but there's methods that can help us out. We can lean heavily on either algorithmic or re-usable plot events, especially if we're making an open-world game.
We have to be careful, though: it's easy to end up feeling flat and formulaic if you lean too heavily on those approaches, and that would completely kill the tone we're going for.
In the end, the tone we want is one where the player can go anywhere in our universe, stop, and just enjoy the ambiance. Whether that means their squad of three is hanging out on top of a methane glacier, in the heart of their starship engineering section, or in a bar on any given space station. We want the player to think "this is a place worth protecting".
Or, at least, "it could be worse!"
There's nothing fundamentally new about these suggestions. Really, I'm just hoping to punch up specific facets that already exist in most sci-fi RPGs.
When those elements get punched up enough, a new genre might emerge. One about existing in a sci fi world, rather than murdering your way through one. But I can't see the end product right now.
I can see making wonders feel wonderful and adults feel mature, though.
I think that'd be a fun start.