I’ve noticed that when you get a bit higher in the ranks the leavers aren’t as common.
On a side note: I HATE playing Genji, but I want the player title: so I was just in a match and won on my first try and boy was it fun! Blade slash after deflect is so cool. Bleading dash makes you feel like a samurai! We went against Zarya so I picked “deflect beams” 
Reacting to the enemy with builds is super fun.
This mode feels like a different game and the more I play it the more I’m obsessed. It’s almost a new game. I think Stadium has a bright future ahead 