Slow updates, not enough heroes per year and too much team-based, it happened the same with heroes of the storm. Really awesome games but sooo team-based that people gets frustrated because you need to be really REALLY good to actually tier up in low elo unless your team is doing a bit of their job.
Last season I played I lost the last game that would have me get into master just because one guy decided we were bad and started to troll. In other games like league of legends you can do some things to win, you have some room to actually get stronger and win (basically permafarming, splitpushing if fits, isolate enemies) but you can't do that in overwatch, and people usually hate that. I love overwatch, I really hope overwatch 2 is better but it won't last if it follows the same hard team-based ideas because people gets bored of looking how they are unable to do anything if one guy decides to throw. This doesn't mean you will always lose everything if one guy throw, you can be lucky enough to have enemies worse than your other teammates and win but that doesn't happen too often.