I second Rimworld. The DLCs literally only add content, and are completely optional even if you own them. In fact, let me shill Rimworld for a second...

Never have I felt every emotion possible from playing a game. From sorrow about one of my child colonists getting gunned down trying to move a rock, to triumph watching a lone colonist single-handedly repelling a mech threat with a bolt action and a sandbag. Rage, watching one of those bastards breakdown from having to sit in a shitty chair and murdering the only doctor in the colony, then dying to the wounds sustained from said doctor shortly after.

Ate without table / 10