Saying he's "not being good" is incredibly unspecific and not very helpful. For the last 2 seasons people with decent numbers are getting paired up with 4-feeder teams on the regular. Sometimes you're on the winning side, sometimes you're not. This is a failure in the philosophy of the matchmaker. Rather than putting you with teammates that have the same understanding you do, you're getting teams that know significantly less. These are going to be 40% of all games. Another 40% you'll be on the winning team. The other 20% are closer to fair even matches you actually have some measure of control over.
For high elo players, it doesn't matter as much, but learning to play through this elo is a shit show, and no player has a chance to learn a better macro when they have a team that doesn't macro at all.
When he's warding, getting his cs, not facechecking the bush, winning lane, or just plain not feeding, he's got 4 teammates that are doing the exact opposite 5 mins into the game. The other team has 3-5 teammates warding, getting cs, not facechecking the bush, winning lane, and capitalizing on his teams feeders. Literally every game is like this now. I feel like 200 years of development experience has done some experimentation on the variables in the system after season 8, and frankly game quality has been garbage since then.