This will also allow you to upgrade your mods to better empower your abilities and survivability. In this stage, you should focus less on unlocking as much of the star chart as possible and more about mods to better empower your frames/weapons.
This is usually when you unlock Jupiter or Saturn. If you’ve reached a point where you cannot complete a mission, then you reached the mid-game stage.
You might have noticed by now that the enemies get tougher with every mission that you complete in each planet.
So you’ve gotten the hang of the mechanics of the game and now you’re progressing from planet to planet.