One thing really aggravates me:
People who abandon a competitive match and leave me all alone. This wouldn't be so bad if Rocket League didn't operate off the blind faith that any disconnection must be purely accidental, and surely the individual will rejoin. Then they don't, and inevitably I can't quite keep up 2 v 1 in a match that frustrated my teammate enough to make them leave. Don't get me wrong, I pretty much always do better solo in a doubles match if I had a partner like this since they pretty much always suck so hard it's kind of amazing, but better when you're three points down one minute in doesn't account for much.
This really grinds my gear though since the game has the audacity to punish your ranking for your partner leaving. I went down a division the last time I stuck around and played out a 2 v 1 match and ultimately lost, and that was pure, unadulterated bs. At this point I just leave if my teammate does because the odds are incredibly high that I'll be going down a division anyways.
Oh, also, Neo Tokyo being in the competitive playlist. It should not be there. All competitive fields should be standard design. I invariably fuck up whenever I end up on the map to the point where I feel bad for my teammate as hit after hit perfectly falls in front of our goal due to the curvature on either side of the goal near the raised sides.