The biggest complaints of survivors and killers
I think I've come to an understanding of the mindsets of survivor/killer players. This of course is a matter of opinion and is not encompassing of all people because people are complex.
That said, I believe the majority of survivor players are just here to have fun. Most survivors (and I guess I could include myself in this category since I started as a survivor main but play about 60% survivor now) just want to go into a match, have a couple of good chases, maybe get some hook sabos right in front of the killer, and if we die because we were outplayed and outskilled, it's whatever. The main thing is, we just want to PLAY the game.
So that brings me to the biggest and most frequent complaints you hear from survivor mains: Camping, tunneling, and slugging.
These 3 things take away the ability for the survivor on the hook or being slugged to actually do anything. It makes the game boring and no one wants to play a game that isn't fun.
Now for killers (and again this is a generalization and doesn't apply to everyone), I believe the overall mindset is focused more on winning and their "fun" is often directly correlated with their ability to win. They tend to be more objective driven and are more focused on kills and end game results.
So for killers, the biggest complaints tend to be: gen speed, powerful survivor add ons and items), and "second chance perks" and the community calls them.
Killers feel matches go to fast for them to get their kills, and they especially feel cheated when a key comes into play and allows someone to escape without getting the doors open. And since they're always feeling pressured on time, anything that allows the survivors to have more time or take extra hits is the worst thing in the world in their eyes.
Anyway, just my observation and opinion on the priorities of the two sides. I'm sure someone will agree or disagree because there's so many opinions in these forums