How do I tell my friend he is awful

So my friend has been playing for roughly a year now and has not improved at all. He continues to button mash A when he gets near the ball, ball chases constantly, and complains about not having any boost while also not rotating to get any (ever). He almost always gets somewhere around 1/3 of my points while saying I’m just “lucky”. The second he seems someone do something like a double tap or air dribble, he wants to forfeit saying “they’re too good”. He sits back almost at our own goal when I’m centering a ball, and almost never is able to make the shot even if he is there for it. He still double commits almost everything, which of everything else probably makes me the most mad. I’m not sure what to tell him other than “I don’t want to play right now” because I’ve told him to watch videos before and he just gets angry.

Edit: To everyone saying “what’s more important, the game or your friendship?” Obviously the friendship, that’s not what this post was about. My question is how can I help improve him or convince him to get better in the frame of Rocket League without coming off as an ah?