You need reasons to do activities in a game. That is what engineer's, factions, poorly implemented powerplay, poorly implemented Thargoid side quests do. Whether you like those reasons and whether you grind to do them (powerplay there is not much choice) is down to the user.
Ace combat 7 has nice weather effects, but you have a reason to fly through those clouds. You would be on mission.
Remove those reasons, and see how long you will play a game for.
Fdev need to add environments, I agree with, but they have to add game with those environments too otherwise they just won't be used.
Atmospheric planets, what's the point in landing on one to get materials when you can land on a non-atmospheric planet which would probably be faster and safer.
There needs to be good gameplay reasons to add them, just like space legs will need good gameplay reasons to add them.
Any kind of mission done on Atmo worlds, be it landing on the surface or attacking a surface installation will bring about more complexities, challenge and danger to the player, compared to airless ones. And it will be a skill based challenge, and not just a statistical one.
That is how they will build upon existing missions and things to do.
After all missions in Elite now are what?
A) - Mine/Transport/Buy stuff and bring them over another place.
B) - Scan stuff on land/space
C) - Kill people
Guardian grind > A
Engineer grind > A
Powerplay > Mostly As, with and Cs
Factions > Same as powerplay
What else new can you implement that isn't A, B or C?
Now add atmo world to it. Imagine a "Scan the surface settlement" mission, but in an atmo world, in a storm, with low clouds.
You already have a challenge entering the atmosphere, because, presumably and logically, you should not be able to enter the atmosphere like you do an airless planet. You would have an optimum re-entry angle and a certain speed range, or you either bounce off the atmo and back into space, or you take heat damage or burn up and explode on the way down.
Now you're faced with flying through a storm, with lightning and crap, and your ship is being tossed about. On top of that, you have atmospheric physics, which means you can't simply boost, and go FA-off and fly sideways. If you do that, your ship will break up due to being subjected to aerodynamic stresses.
Next, as you approach the site, a turret starts firing at you, Guess what? You're in an Anaconda, not a nimble Vulture, because you need an SRV for the mission. It's gonna be a tough call trying to take out that turret in poor visibility, and subjected to an aerodynamic flight regime. You turn like a pig, can't really get a proper shot off, and are getting pelted heavily in return. You're gonna have to land somewhere far away and deploy the SRV.
Ah, next, landing in high wind (storm, remember?), your ship is tossed about and you're having a hell of a time keeping it level to the ground after finding a small spot just flat enough to accomodate your Conda. A bit to the left, and it's too angled.
After you've deployed your SRV, it is also subjected to poor visibility and high winds. And oh yes.... it's a storm. Raining 'Goids and Guardians. Poor traction. You find yourself slipping and sliding all over the place, which makes things hairier when avoiding the turret fire as you approach the installation. Using your jets in high winds is hell too, because the moment you're airborne, hurricane force winds will toss you wherever it deigns fit.
Now, contrast that to a surface scan mission on an airless rock.