Objectives do not need to be unnecessarily complex.
Collect an object: Capture the Flag, Stockpile, One Flag
Secure an area: King of the Hill, Plots, Territories
Deliver an object: Assault, Ricochet, One Bomb
Kill players: VIP, Juggernaut, Headhunter
Gametypes do not need to be overly complex.
Weapon specific: SWAT, Snipers, Griffball
Vehicle specific: Race, Rocket Race, Hog Potato
Simon says: Fiesta, Sharp Shooter, Gun Game
Asymmetric teams: Murder Mystery, Infection, Invasion
Even Invasion, one of Halo’s most complex gametypes, simply combines existing objectives into a larger, multi phase battle. Complexity through simplicity.