Sins 1 always was more of a RTS (or the eXterminate part of 4x) type of game. But Sins 2 has improved on it already.
- Excavation is already more interesting, and it's very likely that artifacts will be added.
- There is derelict loot to be found scattered around the map.
- It is important to find the minor factions now, including pirates.
- I really hope more types of planets (most non-colonizable, like we had in Sins 1) will be added, this adds to the exploring as well.
- More options to planet and ship customization are also already included.
- The orbital mechanics also add a deeper layer to the game, while not specifically in the 4x part it does very much fit in my opinion.
And it's always nice for the devs if you have some concrete suggestions to share! 
