If you are a casual player who games all by yourself, don't bother getting Overwatch. On average, you will be losing seven or eight out of every 10 matches. How is that fun?
To do well and win in Overwatch, you must play with friends. Good communication is crucial to winning games. By talking with friends, you'll have a game plan all set up, which will increase your chances of doing well and winning. But if you're playing solo, you can forget all about that! You can't really communicate with your teammates, because people rarely use the game's integrated communications system, and the community is so toxic that communication tends to break down even if you do.
So you have no idea what to do and are then forced to have a game plan all by yourself. And that will almost never work because it's a team-based game.
You might be thinking that the obvious solution is just to play with friends. But there are lots of players out there (like myself) who don't know anyone else who plays Overwatch. Most of my friends either quit or play with such rarity that they basically don't play at all. And some others don't want to plunk down $60 for such a truncated experience.
I could search the internet for randoms to play with, but that's tenuous at best and rarely turns out like you'd hope.
There really is no way to combat this or cater to solo players, because Overwatch is a team-based game. You need cooperation, and there is no way around it. Maybe if the community were better (or matchmaking took factors like communication and cooperation into account), then it wouldn't be such an issue.