I'd like to recommend you all this video by Extra Credits. It explains a little about random chance in Esports, and makes some suggestions on how people should handle it.
Think of your teammates as a random factor. The thing with random chance is that it can
and will go both ways eventually. While the better player might lose a given game due to bad luck, they will, over time, win more matches than a lesser player.
If you find yourself losing constantly, then you might in fact not be that good a player yet. Keep in mind that in Turf Wars, your point total only counts how much turf you've painted. That's a nice way to encourage people from just going after useless splats all the time, but it's not a very good measure of how much you've contributed to the team effort. If you paint a lot of turf, but the opposition easily claims it back, you've scored a lot of points, but contributed very little.
I myself went from C- to B- in about three, four hours of playtime. I knew what needed to be done, picked for myself a role that would help get it done, and fulfilled that role quite successfully. There is no way I just happened to end up on the winning side that often, so I have absolutely no qualms about claiming that I was the better player on the field during that time.