I have this thing when people ask me what I think about a particular religion. It doesn't really matter the religion, most of them have a mix of good and bad messages, probably due to the slanted views of the translators and scribes who copied them again and again over the years, but in general I don't have any problem with the religions themselves. It is the people who subscribe to the religion in question that I usually take issue with.
The same holds true in Overwatch, and if anything I would say that it's a simple but pervasive issue.
Overwatch is an amazing game, with wonderful graphics, artful storytelling, a unique cast of characters (aka heros) and an interesting, albeit sometimes frustrating, series of maps to fight on. Teams square off each other, and the ones that have a combination of good players alongside good hero synergies often ends up winning each match.
That second portion - good hero synergies - is often a point of contention. It takes time, patience and a relatively steep learning curve for most players to figure out that certain heros work best alongside other heros, and that for a team to succeed they usually need at minimum one supporting hero and one hero designed to absorb or block incoming damage. Unfortunately, most players want to choose a hero that is designed to deal damage, and they often cannot play that hero effectively, due to the aforementioned missing team composition elements.
The worst toxicity, however, tends to boil out of those players who choose a damage dealing hero and play that hero very well, but are unable to carry the rest of their team to victory. Because of this, more often than not, those players immediately blame their teammates, curse them out, rant over text and voice chat channels, and then subsequently throw matches in an attempt to "punish" the other players on their team, dragging everyone down into their spiral of toxicity.
When toxicity boils into voice and text communication, it ruins the match along with the fun of everyone involved. It can linger into subsequent matches, long after that player is no longer around. While Blizzard has been making improvements to the game in an attempt to combat these issues, many of them seem too little, too late.
I first stopped playing Overwatch about a month after I started playing the game primarily because of the toxicity issues outlined above. When the Uprising event came out, I decided to give it another shot, because I thought that perhaps if I really spent time and energy and learned how to play the game well, learned how to participate with multiple heros, gave "Competitive Overwatch" another chance, then eventually my self-improvements alongside the Blizzard social interaction improvements would somehow make the game fun again.
More than a year later, I can say with certainty that I was wrong. I'm sorry Blizzard, but whatever you think you've managed to do to make this game better and reduce the toxic playerbase, it's not nearly enough. I don't know that I'm ever coming back. Good luck (you're gonna need it).
Rest in peace, site banner.