Well Queta is another story entirely. Someone screwed up there; Monte, Brown for developing him in the G-League for 2 years and then just letting him walk. And he's played 15 MPG for the Celts in 34 of 42 possible games.
Everyone else being bad, doesn't make Len "better".
Len was always a guy who should be used in spots, when they need his size. Not a guy to go to every single game, in a routine rotation, because with today's teams the smaller "stretch" 5 or power forward at the 5 types are played often.
The mistake is to not use him in his best spots, for whatever reason. Like when you need to minimize a guy like Valancunius. Again, the difference now, is that Christie won't hesitate to use him in a spot when needed, whether or not he hasn't played in a game or two.
Use your small ball 5, along with your full sized center, to fill out a flexible rotation from game to game and in different situations within game