I see Brown as really having come of age this season, and it is especially apparent in this playoff run. He is a force on both ends of the floor, albeit rough around the edges at time. But he signed his big contract and got better. He may well be the best #2 in the game, certainly the best #2 left in the playoffs.
But what I think is really important is his "I love my brothers" stuff. You first saw it with Porzingis, he embraced Porzingis and I believe that helped Porzingis integrate with the team. You hear him say things about his teammates and then what the teammates say back. Tatum is the leader and best player on this team. But he is not a "love you bro" kind of guy. That is Brown. Not exactly KG but a little bit of that in him. I don't think Tatum is any less loyal or whatever to his teammates, but Brown is more outward about it. It is impacting team chemistry in a positive way.
As to the individual Net ON/OFF +/- stat, I have doubted that stat for a while. I did an analysis of Porzingis in his injury thread which shows the impact of who is ON when a player is OFF. Or who else may be OFF when the player is ON. I am not sure what is going on with Brown. But if you look at playoff 2 man stats, Brown is negative when on the court with Pritchard and Kornet, kind of neutral when on the court with Hauser, but very good the rest of the time.
I don't know how anyone can watch the recent playoff games and not think that Brown has been a major factor in winning. I can't figure out why the Net ON/OFF +/- stats don't reflect this, there must be something wonky going on. But I am all in on Jaylen Brown.