There's a game design concept I haven't seen used much. It's a way of designing exploration/open-world games. It requires algorithmic content, but that's pretty common these days, so I think we'll see this concept become more and more common as well.
Let's discuss a game like Spore or No Man's Sky. The game is theoretically about exploring space and discovering wondrous things.
The problem with these games is that there really aren't very many wondrous things to find. It's mostly just an endless array of the same things with slightly different aesthetics.
But it can be made much more interesting using the "Investigate & Expand" design.
In this mode, when the player stumbles across something they find interesting, they have the option to explore it in more detail - investigate it.
For example, if you find a space village, you can go to their cities or talk to their people. This is a different scale of exploration, allowing the player to choose to get closer to something they might find interesting. Or not, if they don't find it interesting.
Some games certainly do this. They generally stop there. But you need a follow-up. You need a reason why investigating matters.
That's the second half: Investigate, then Expand.
Once you've investigated something, it integrates into local space and you can help it expand. For example, the space village will contact you whenever you visit a star near their space and give you an optional mission - "can you find a plant we can eat?" "We have an abandoned base there, can you set up a beacon on it?" "One of our ships is damaged near there, can you find it and rescue the crew?"
Completing optional missions expands the space village - a larger home base, a new colony in that star system, etc. Which, in turn, means more missions over a wider swath of space.
This is a one-two punch: investigate something interesting, then help it expand if you want.
The expansion phase is extremely powerful, because it gives you a new context for any barren hunk of rock you stumble across. People and things you've chosen to help have a vested interest, so you have a vested interest. Whether it's something simple like tagging resources or something more complex such as finding a crashed ship, your exploration now has a context. You are here to help - or to choose not to help.
Exploration is also powerful because you can have multiple missions from multiple people as expansions continue. "We have a crashed ship in the area", one says. The other says "we're in the area, could you carry us some supplies?" Depending on your engine, you could even make the missions intertwine - you can only complete one, or both are from the same cause, of whatever.
It's easy to start imagining advanced algorithms, but this can be done with very simple algorithms. The algorithms for the missions can be simple, that is: the algorithms for the space villages are significantly less simple.
Every space village would need to be unique enough that players would have an opinion on them, specifically. Moreover, every space village would need a presence with particular needs and practices, so that as missions are accomplished they could organically expand. Moreorover, you would need to allow for investigating again, after a time, and discovering those new growths and changes.
I don't think these are overwhelming technical issues, but let's talk about a short cut: an open-world fantasy game. Skyrimlike.
The various party members you accrue can be "investigated" by talking to them. More advanced investigation might involve unique level-up patterns and algorithmic reactions to situations in the world, but let's leave that for now.
The expansion phase is also relatively straightforward. Instead of gaining XP by killing monsters, characters gain XP if you complete sidequests for them. The things each character cares about and the kinds of missions they request are preprogrammed, but these are not scripted missions. Rather, they are a simple framework: you enter a city, the urban thief gives you a mission to steal from a specific too-rich noble. You enter some woods, the elf gives you a mission to find as many glowing lichens as you can. Enter a different city? A different noble. Enter the first city again? A different noble. Different forests? Different plants.
The reward for each? XP.
These missions could be made more interesting because the characters are actually with you. As you get close to the noble, or wander near some lichen, the character that gave you the mission can pipe up with advice or commentary. Perhaps they gain a stat bonus while you are "on" their mission. It can all be quite generic: no advanced dialog engine is required.
You can then directly tie their level to how much they trust you, such that their next dialog option becomes available with each level.
This system requires no generative world content. Helping the thief doesn't rearrange the politics of the city. Helping the elf doesn't establish a new elf stronghold. It's very simple, very shallow, very easy.
It's the same thing. Investigate and expand.
I think it's a good design concept, especially if you have a lot of chaotic content. For example, if you allow players to create/share NPCs for your fantasy open-world game, you can rate each NPC by how high a level the players usually help them reach. The higher the hit rate, the more appealing/interesting the character is likely to be: probably a good choice to put in a new player's world. Less popular/new NPCs can be put in the worlds of more experienced players.
The same is true of alien civilizations. Same thing.
Well, those are my thoughts on the matter.