Stellaris, while it's a known game from 2016...
There actually have been several large expansion packs which made it better, and harder to survive in, as well as bringing a feel of an "endgame" more than just taking over many planets until you are all alone.
Starting with story expansions that makes things more interesting than just "kill or be killed":
More race options, as well as the beggining of the threat of "life" in the universe:
Adding end game ships and power:
Ending with their latest trailer from an expansion going out right now these days, apparently to make things even more interesting:
There is more to this game than just the original, so it looks worth playing over again (or start playing it), not considering it as a finished game that's from the past.