Crusader Kings has no win condition, but there are a million things to do. In Stellaris, once you complete the early game and gobble up all the unclaimed territory, your options are to wage a war of expansion or do nothing. Science is only useful for gathering more minerals and building stronger ships, there’s no wonders, no culture victory, just war. Zero-interactivity “throw your stack of doom at their stack of doom and cross your fingers” war.
You can’t even accumulate resources because there’s a cap on stored minerals, if you’re not going to war or expanding your empire, you’re clicking “next turn” without doing anything.