It bills itself as a 4X game, which works if you're willing to count combat as extermination. If you house rule wiping out all of a player's planets, then exterminate would be more realized. (Really, classic 4X exterminate means colonial style genocide) But that would turn the game into pile on the first person to show weakness so maybe we don't need that much extermination.
Mechanically, it's a skinny deck Race for the Galaxy with Cosmic Encounter's combat. And that's where the rub might well be. Race for the Galaxy is one of the best games I've played and Cosmic Encounter is a multi-generational classic.
In particular, Universal Rule and Race for the Galaxy take about the same amount of time. And if you leave the box behind, Race won't take up much space in a courier bag or backpack or the like. So Universal Rule's size advantage really just makes a difference if you're limited to your coat pocket. (Which to be fair, I sometimes have been)
I suspect that, if Universal Rule is to break into regular game rotation, the selling point will be in the combat. Since it is resource heavy, you're going to have to work your way up to attacking someone but everyone at the table gets involved and it can be worth a hefty six points. So when combat happens, it's going to be a big deal.
Universal Rule actually runs into an issue that I don't often to see in micro games, which is that the small size of the game might interfere with the complexity of the game. Adding another card as a player aide, that would solve that though and the instructions include that.
It also runs into the issue of being a micro game you'd play instead of a larger game. You wouldn't play HUE or This Town Ain't Big Enough for the 2-4 of Us instead of Carcassonne. They take about a fifth the time or less. I have to choose to play Universal Rule instead of Race and that wouldn't happen with my old Chicago crew.
At some point I need to play Universal Rule. It is a micro game that fills a non-micro game space. Can it step up?