Play The Objective
Overwatch is not your typical FPS where the goal is to rack up as many kills as possible, it is an objective-based game that requires great communication and team effort in order to win.
The four main game types in Overwatch are Assault, Control, Escort, and Hybrid.
In Assault, you and your team must capture two points on the map in sequential order while the other team fights to defend them. Control is somewhat similar, but rather than one team playing offense or defense, both teams are targeting the same point of control until one side gets it to 100%.
Escort requires the team to follow a payload to the end of the map in order to win. Finally, Hybrid is a mix of both Assault and Escort, where you will capture a point, then escort a payload to the end of the map.
One of the most frustrating things for any team is to have someone who is fixated on getting eliminations rather than playing the objective. Do not be that player!
Stay with your team, attempt to group up with others and communicate to your team so that you can orchestrate a well thought out plan of attack.
Always focus on the objective first, then worry about getting eliminations as they come. Sure, getting 50 kills is great for your personal stats, but if you lose the game, does it really matter?