head to head
Neither is simply harder - they are hard in different places. DOOM (2016) demands more optimization; Rocket League demands more reads.

Execution · Pure Mechanics
Push-forward arena FPS where movement and aim are the whole game.

Execution · Pure Mechanics
Mechanical car-soccer where execution is the ceiling.
DOOM (2016) leans Execution (Pure Mechanics); Rocket League leans Execution (Pure Mechanics).
Rocket League leans clearly harder on execution.
DOOM (2016)
Aim, movement, glory-kill timing all peak.
Rocket League
Aerials, flicks, dribbles, pure mechanical ceiling
Rocket League leans clearly harder on reads.
DOOM (2016)
Demons scripted attack patterns.
Rocket League
Rotations and 50-50 reads against humans
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
DOOM (2016)
Minimal encounter randomness.
Rocket League
Almost deterministic physics
DOOM (2016) leans clearly harder on optimization.
DOOM (2016)
Rune and weapon mod picks meaningful.
Rocket League
Training routines, rotation theory
A matching score does not mean a matching test. Two games can both sit at 10 on execution and demand completely different things of you - which is why the reasoning above matters more than the number beside it.