I can't speak for everyone, but nothing immerses me more into a mission than good text......& preferably verbally given, rather than text.
With that in mind, I feel a lot could be done to "improve" missions, simply by making the various levels of text more immersive. There are three key elements to this IMHO.
Remove Superfluous Words from Main Mission Titles: I keep seeing this over & over. Mission titles that have utterly irrelevant titles tagged onto them, as illustrated below. Other such irrelevant words are things like "Agricultural Liberation of....." or "......in the name of Democracy". All these superfluous words should be removed from the mission titles, as it really takes me out of the moment. The only ones which should remain, in general, are those words that refer to the Faction State-like Outbreak Missions, Civil War Missions etc.....& even then only when completely relevant to the type of mission.
Add more Variety to the Text Description of the Mission: This refers to the text I've 'circled' in the picture below:
The text description of these missions could be selected from a handful of half a dozen different options, with strings used to individualize it even further. So, instead of only saying "We need you to deal with this surface salvage operation for us", you might occasionally get something like "One of our pilots was recently rescued in <$System Name>, sadly we weren't able to find his cargo, & we were hoping you could find it for us", or "News has reached us of a potential salvage opportunity in <$System Name>, care to confirm it for us?" Basically, the computer would choose one of these half a dozen options at random, so as to make this text feel much less repetitive.
Use Inbox Messaging for all Missions: Though not perfect, one of the things I love about Follow-on missions is the inbox message you get after accepting the mission. It really does help with immersion, as that text goes into much more detail. It also turns up in relation to Surface Scan Missions. as seen below.
I would love to see this kind of inbox text for *all* our missions, whether primary or follow-on. Like my suggestion above, you'd need about half a dozen different options for the computer to choose from, with strings used to further individualize the message, to ensure that the messages never feel too repetitive.
If all 3 of these things were done, I feel that missions would take on more life for many commanders. It would certainly aid my suspension of disbelief.
With that in mind, I feel a lot could be done to "improve" missions, simply by making the various levels of text more immersive. There are three key elements to this IMHO.
Remove Superfluous Words from Main Mission Titles: I keep seeing this over & over. Mission titles that have utterly irrelevant titles tagged onto them, as illustrated below. Other such irrelevant words are things like "Agricultural Liberation of....." or "......in the name of Democracy". All these superfluous words should be removed from the mission titles, as it really takes me out of the moment. The only ones which should remain, in general, are those words that refer to the Faction State-like Outbreak Missions, Civil War Missions etc.....& even then only when completely relevant to the type of mission.

Add more Variety to the Text Description of the Mission: This refers to the text I've 'circled' in the picture below:

The text description of these missions could be selected from a handful of half a dozen different options, with strings used to individualize it even further. So, instead of only saying "We need you to deal with this surface salvage operation for us", you might occasionally get something like "One of our pilots was recently rescued in <$System Name>, sadly we weren't able to find his cargo, & we were hoping you could find it for us", or "News has reached us of a potential salvage opportunity in <$System Name>, care to confirm it for us?" Basically, the computer would choose one of these half a dozen options at random, so as to make this text feel much less repetitive.
Use Inbox Messaging for all Missions: Though not perfect, one of the things I love about Follow-on missions is the inbox message you get after accepting the mission. It really does help with immersion, as that text goes into much more detail. It also turns up in relation to Surface Scan Missions. as seen below.

I would love to see this kind of inbox text for *all* our missions, whether primary or follow-on. Like my suggestion above, you'd need about half a dozen different options for the computer to choose from, with strings used to further individualize the message, to ensure that the messages never feel too repetitive.
If all 3 of these things were done, I feel that missions would take on more life for many commanders. It would certainly aid my suspension of disbelief.