He's a facilitator. Let's remove assists per game stats out of the discussion. I get your point. Assists per game doesn't always reflect whether a player is a good facilitator of the offence.
Ok, maybe, for the sake of discussion, lets say that assists per game is not the stat to look at. Because you are right, that stat doesn't always reflect a players ability to facilitate the offense. But Rubio is a facilitator of the offense, as is all NBA point guards. It is their number one responsibility. To either get the ball to a player that can score, or for that point guard to put points on the board himself. Assists per game will not break down the efficiency of facilitating the offense. But there is another stat that will. Player efficiency rating. This is a stat that doesn't lie. It reflects a players per minute efficiency rating of numerous stats.
Rubio is ranked 223rd in the NBA at 12.52 PER. There are only 347 available rankings in the NBA. Rubio's on court production is horrible. The great thing about the PER stat is that coaches can use it to maximize a players on court efficiency and adjust playing time accordingly. If they are playing a guy more minutes than normal and the stat dips, it tells you that that particular player is playing max efficiency under X amount of minutes. Just because someone is coming off of the bench and has a better efficiency doesn't necessarily mean that they need more minutes. It just means that you can evaluate how many minutes to play them and extract the maximum efficiency.
Jazz players ranked higher than Rubio are
#207 Joe Ingles @ 13.03
#198 Raul Neto @13.31
#186 Jonas Jerebko @ 13.66
#153 Rodney Hook @ 14.68
#133 Alec Burks @ 15.25
#127 Ekpe Udoh @ 15.59
#107 Thabo Sefolosha @ 16.22
#90 Donovan Mitchell @ 16.99
#57 Derrick Favors @ 18.80
#37 Rudy Gobert @ 20.08
One thing about analytics, math doesn't lie.