This one ties in with the previous point that I made. One of the main (if not the main) reasons why I would lose so many games in a row was because my team was either completely out of synergy, or had no idea what to do.
One example that I will never forget was when I was playing as Lucio, and my team had to escort the payload to its destination. My teammates were taking damage, so I rushed to them in order to heal them. As soon as I reached them, all of my teammates that were on the payload split up for no reason, with barely any health, and proceeded to die before I could heal them. And since Lucio is not an offensive hero, I died almost immediately after my teammates because I had no one to protect me. This is the prime highlight of my terrible experience with random players.
Sadly, this is too common in Overwatch. Random players have no idea how to cooperate and communicate in order to win. How can they? They don't know one another, and are obviously not in a party. But this isn't the only example.
Another reason for losing so many matches comes from having no team synergy. A lot of times, my team was composed of heroes that had nothing to do with each other, almost like all of us closed our eyes, and proceeded to pick a hero at random. Worse, very rarely would we switch to other heroes, which by that time was too late, since we would lose seconds after.
I always tried my best to choose the most appropriate hero that would greatly benefit my entire team, and give us some sort of chance to win. But unfortunately, everyone would drag me down by dying, or by not playing their role, which would result in confusion, frustration, and losing.
An effective solution to combat this issue could be reworking the matchmaking system to such a degree so that it puts solo players with and against other solo players, and parties against other parties.
If a team is composed of solo players who aren't communicating, don't have a game plan, and simply don't know what to do, against other solo players with the same disadvantages (or perhaps, advantages if you want to look at it this way), this creates an even playing field where everyone is basically equal. In return, solo players won't have to feel bad about themselves, and know that they are playing with/against others who are just like them! As a result, this creates a sense of equality among "solo-ers," sucky players, and beginners.
But, if two parties go against one another, this too can be applied to them. Since everyone will be talking and communicating, the teams will in fact have a game plan set up, and that as well will create an even playing field, just how it'll be created for solo players.
It's a definite win-win situation for everyone. Teams will play against other teams, thus creating a somewhat of a competitive environment for them, while solo players won't feel discouraged, and know that they won't get steamrolled by a cooperative group.