Ummm, no. Kyrie improved playing with Lebron (and Lebron let him be ball-dominant, to the point of having a higher usage rating than LBJ his last year with us). Delly improved and Lebron was willing to play off ball with him -- if he'll do it for Delly he'll do it for anyone. Cedi would improve if we played him. In Miami, Lebron was even able to make Mario Chalmers look like an NBA player, which he instantly stopped doing when Lebron left. Back in the day Lebron developed Varejao, Boobie Gibson, and other players who wouldn't have had much of a career without him.
There are two big reasons it might appear that Lebron doesn't develop young players. First, he has been the most unlucky superstar in NBA history in terms of the rosters put around him -- he's either been victimized by the crap Cleveland front office and our terrible inability to build good teams with him, or he was on the Heat who had totally cleaned out their $$$ getting the big three. Second, he goes to the Finals every damn year and it's hard to develop young players when you're doing that.
If you think we have some great playoff team based on ball movement if Lebron and Kyrie weren't on the floor, ask yourself what that team would look like. At what point have this version of the Lebron Cavs had a secondary creator who could reliably function without either Lebron or Kyrie on the floor? Without Lebron our starting lineup on this squad would be:
PG George Hill
SG: Smith, Clarkson, or Korver
SF: Cedi Osman or Kyle Korver
PF: Kevin Love
Center: TT or Nance
On what planet does that team even make the playoffs?
Lebron has been cursed with having to deal with a Cleveland front office that wastes resources recklessly and has no idea how to spot or evaluate talent.