Klomp, Rubio's passing numbers were bad the first season with Utah because:
A) He was asked to shoot more. Career high in shot volume. More shooting, less passing.
B) Snyder's system is like poetry in motion, compared to Saunders **** on a stick. Ball moves, players move, every player knows exactly what he's doing, and assists are shared. Lots of hockey assists. Several players averaging +4 assists, none even dreaming about getting 10. You mention Mike Conley. You know he sucked and was even benched? You know he averaged 4 assists/game last season? Yes, it was Teague 2.0 in Utah and Jazz fans quickly hated the trade.
C) Rubio had clear orders to feed Gobert. Gobert is no Towns. His offensive game is limited to dunks and putbacks and he's got hands of stone. Rubio really struggled to get the ball to Gobert for months and turnovers piled up. They started the season IIRC 11 games below .500 but finished 29-6.
All in all, you can't compare that situation to this one. That was a very complex system.
That 1st season you mention, Rubio shot
42/35/86 for a career high 13.1 points in 29 minutes. The system allowed him to take quality shots.
Now he's shooting
34/18/82 for 6 points in 23 minutes. He's forced to take terrible shots because nobody moves and nobody knows what to do and what the other 4 teammates are going to decide to do on the fly.
Watch this. You won't believe it until you see it: