I love mayhem and I hardly ever see it anymore sadly. My second is team deathmatch but mayhem was always my go to. I had so much fun there!
I do hate mystery heroes. Random my ass. That thing made me play only zenyatta and doomfist for like 6 rounds of deaths. It needs to be fixed. Maybe making sure if you die, you spawn as a new hero that is not currently on the team and you do not get the same hero so many times.
I miss the rotation Arcade.
No choices, just play. And the modes were better too. All soldiers with low health on Lijang, Only Genji/Hanzo on Hanamura, or only Tanks/Support.