It makes them better, but not better to where they'll be contending.
The other real downside to Jimmy in this offense is that he doesn't stretch the floor, which they've been in desperate need of all season. But that can be mitigated somewhat by the fact that he knows how to survey the floor to a far greater degree than Wiggins did. He's aggressive, whereas Wiggins isn't. He can get to the FT line and stop the bleeding, which has been one of the team's weak spots for a minute, which Wiggins rarely ever aided in (never mind the fact he's a terrible FT shooter).
He's a competent secondary playmaker, whereas Wiggins isn't. He can get his own when the game slows down in the 4th, which has been an ailment of their offense in the clutch this season, whereas Wiggins struggled to have any real impact when they needed a bucket down the stretch.
He generally has a much higher BBIQ than Wiggins too, so the offense should flow more organically once he gets settled.
Having another alpha on the team will also means opposition teams will treat them with more respect, and that should help alleviate some of the pressure that Steph has been under this year. Now Steph will have someone else that the defense has to focus on, and not have all eyes on him.
