Then you just conclude that Green is a useless player hehe. It's not about the productivity but the overall performance. It's common to lose that everybody in Warriors is struggling. If he is nothing without Steph and Klay, then no team will have interest on signing him in the future and worst, the Warriors might consider trading him despite he is a part of their championship run. I didn't even hearing his name in some rumors that a team shows interest to him.
It's true. Overall performance can keep you in one team even if you are not a shooter.
Then, there is impact, being a team player and so much more to offer than just being an offensive player.
Look at KD, he had been jumping in different teams and so does Kyrie and Kawhi. They are not the type to be a team player but mostly isolations.
Playmakers such as Draymond Green and Marcus Smart are different. They may not be ball handlers or with high dribbling skills but they can manage the plays and can lead using high IQ. Lebron is doing the same thing when he got older.