TL;DR
Create a system to make the planet feel alive and give players random objectives that have random rewards.What?
The concept of crash landing on a planet is super cool but the player is totally isolated. I propose that a "community" is created that the player can "talk to" -- i.e., the player is in contact with NASA and/or there are other "players" that also crash landed on the same planet. To be clear I am NOT proposing that this community is real in the game, rather that a technology is created which allows ET to phone home, and for home to phone ET with requests. For example, the player is in the middle of automating blue science and gets a notification that NASA would like some biological samples from biters... which requires the player to go and eradicate (2) biter nests, or n-number of nests where each nest has a % chance to drop a requested item (e.g. a biological sample.) Then upon gathering all the materials and launching them in a probe home (or a probe to another community on the same planet, or a nearby planet, etc.) then the player is rewarded with some type of resource that can only be earned through these missions.Why?
You build this super cool base, and everyone knows the objective is to launch a rocket, but you can take as long as you want to get there, or you don't even have to get there and can play forever. Which is cool, but it makes the game feel very lonely and empty. No one is trying to find the player, no one is talking to them, and if the player doesn't generate much pollution then the biters do nothing. Having random missions that the player can opt to take or refuse adds a new dynamic atop the existing structure and gives new purpose/entertainment. Basically it gives you a reason to keep playing. The rewards from these types of mission can be purely quality of life improvements, or cosmetic. Better weapons that can only be obtained through the missions, or niche technologies that don't really impact or effect the game at all other than being cool/making life easy. Perhaps create a "store" system where the player can buy commodities with a currency earned from these missions. E.g., the player might get a notification that an NPC on the same planet (or a nearby planet) requests 100K iron ore. The player needs to create a production line, mine the ore, and then send it off on a mini-rocket. Upon completion the player is rewarded with 100 credits which can be spent buying cosmetic items, or can be used for the player to request help from other NPCS --> e.g., for 200 credits the player can request 100k uranium ore to be delivered to them within 1 hour.Just a thought. Love the game. Reminds me of playing Privateer.
edit: As a final thought this idea could also act as a tutorial. I hate games that have tutorials. I hate games that are so difficult that you need to play the tutorial (cough, Crusader Kings 2). I hate games that force you to play the tutorial even more (cough, Fallout). I love both of those games, but I really HATE tutorials. Factorio is cool in that you don't really have a forced tutorial, but you do kinda need a short tutorial and you guys did a good job with this in terms of orientating the player to hit the ground running with the pre-made scenarios. I really appreciated that. I could spend like 5-10 minutes in your tutorial, which itself was fun & interactive, and then get turned loose in the game. The gap is once you master the early game mechanics and start getting deeper in the research tree. It almost feels like I need a separate tutorial, but a non-mandatory one. I can complete the game without circuit networks, for example, but it just takes a lot more time, is a lot more boring, and it means missing out on a lot of content. One of the most brilliant parts of the game is that you can decide how you want to play, and there are a lot of technologies which are optional. By having a mission system/network that allows the player to interact with a larger invisible NPC community you can also incentivize players to experience content and learn new game mechanics. Maybe there are some biters that swim and can only be attacked if you research something optional. Maybe the only reason the aquatic biters exist is to satisfy certain missions, and in no way impact the overall goal of completing the game. Randomly a mission pops up asking you to go kill 100 underwater biters... but that means you need to research something... then you need to build a mini-underwater base... then you need to research more... then finally you can fight them... and after you complete the mission you get something out of it. A cool camo pattern that lets you move like Predator and makes you invisible to Biters, or maybe some custom weapons like a .357, sniper rifle, etc. Would be super cool to have a .308 and be able to pop off biters at a range that is so far they can't see or attack you back... but only if you have a special rifle, and a ghillie suit... and then of course there might be some kind of mission to go in and assassinate a leader of the Biters for a mission, etc., etc., etc. It could really add a lot of depth to the game without overhauling the core game or requiring many (any?) structural code changes... but then that is just an assumption
e2: Could have missions where you agree to do something and the result is that all biters on your planet want to kill you. Like you accept a mission to protect a special item that someone else will pick up in 1 month, but during that 1 month there will be constant attacks from distant nests because your pollution increases by n% but if you complete the mission then there's a blast and all the waves of attackers die and the game goes back to normal. Come up with a dozen or so styles of missions and then randomize their availability/quality of rewards from them to make it in the players interest to always be checking for new ones.