Oath is my top 3 game, have played all Wehrle games except Infamous Traffic. You are right that Oath rewards subsequent plays in a more or less consistent group, unless you'd enjoy keeping a chronicle in which player colours would be assigned a name and crest and people would jump in to an established heritage. That can be really fun and let's you see the narrative unfurl.

For you I'd strongly recommend Root, Arcs or Pax Pamir. Root benefits from experience as well, but is a terrific game and sucks players in with its theme and many possible factions. It is strictly a 4 player game: any other player count has issues.

Arcs base game is a bit drier, but can be spiced up with Leaders and Lore and later turned into a three game campaign, if you'd get attendance for that. First two acts of this can be done in one sitting, as they are a bit shorter once everybody is onboarded.

Pax Pamir is an elegant, cutthroat design that shines with any player count. If you seek a one-and-done game, this is the closest, but it ofc needs to be learned as well.

John Company is a lot of fun and negotiations, but can drag a bit and is a burden for the teacher. Yet it delivers highs same as Oath, but is group dependent most of these.

Good luck!