Teams are running under the screen with Rubio (not with the other guys and you'll notice that when other guys run PnR with Rudy it looks a lot like last year) and daring Rubio to take shots that he is bad at. Rubio can't put pressure on the rim at an NBA average level, and he can't make teams pay from deep. The result of that is that the defenders can cheat to Gobert and make the action much more difficult to produce a good shot for him. But even with that there are still plenty of times where there is a team rotation down to guard Rudy and it produces an open 3. On top of that Rubio is apparently terrible at throwing lob passes. They are always behind or get picked off because the defense is set.
Rubio is the reason that the PnR isn't working, with a small dose of bad spacing because of the lineup. You can overcome being a bad shooter if you can get to the rim, but you can't be bad at both things. The one thing that Favors can do with Ricky is that he can play a pick and Pop game where Ricky seems a bit more comfortable making that kind of read. Of course a mid range shot is not very efficient, and it takes the player out of rebounding position as well. Favors played well last game, but the Nets were playing a small lineup.
But I guess the main point is that Rudy is still creating the conditions to get open 3's, but Ricky's anemic PnR ability is making it less frequent. After the first couple games he just stopped passing to Gobert at all in those situations.