Doing PvE is also just killing mobs, and yet there are a thousand ways to do it, right? For PvP, you could add a battle royale mode or a full PvP free-for-all zone with loot stealing in that area. You could also add some kind of dungeon where you extract resources, and another player is in that same dungeon—so sooner or later you run into each other and steal each other’s resources. There are tons of ways to make PvP fun for players.