Couple reasons for me while I am only playing the odd game of overwatch this season.
Ranked is horrible at the moment. Last season I noticed an increase in trolls and this season has really pushed me over the limit. I don't get to play a lot of games due to work and when I get home I'm honestly too tired. But going into ranked games at High masters/low gm and just praying that I don't have someone who will give up or troll when things are not going their way is not something I should have to worry about.
I hate dive comp. Never have I felt so useless this season as someone who enjoys playing the healers characters over the others (except mercy will get to her soon). You have to pray that your team will react and help you if you get dived and pressure them off you. IMO dive makes so many characters useless if the enemy team can play it correctly. Like I have seen other people say it's really upsetting that pretty much half the characters are out of favor and just no really worth playing and I completely agree with them.
I know on this sub redddit there has been a ton of about mercy but I just have to add to it. I enjoy this game so much more when she isn't on either teams. I feel the game flows so much better. In my opinion she's going to be very hard for Developers to get her to a stage where she's isn't a nightmare to play against. I disliked Rez since the games release really not fun to play against when this game is decided a lot of the time by ultimates. I can't remember the last ranked we're a mercy hasn't been played.
The ranked system is so bad. Me and my friend were talking about the league ranked system in comparison to this. I believe win streaks at the moment aren't nearly as good as they used to be but even still. I know we have all had that feeling when we hit rank we have been aiming for it feels great but for me it doesn't. I know a lot of people will disagree with me but i prefer the long ranked system in league and to be honest the way it works stops people getting to ranks they don't belong in. I find it kinda crazy that if you have an amazing day of overwatch you can climb from say masters to gm in the space of a few hours. Like do you really deserve it just feels weird to me that you can climb so fast. I just don't don't it rewarding to be honest. Plenty of people have touched on sr gains and how they make no sense, i agree with that completely. I have no idea why the base your sr gains off your performance in a 6v6 team game where team work is so heavily required.
Sorry about the long post just needed to get this out my chest:)