Could be a combination of the two, honestly,
I would say it has more to do with him being a starter, but definitely a combination of both.
Bradley and Crawford were good for 30+ shot attempts in every game. That extra 30 shots means a lot for less aggressive guys like Green and Wallace.
Wallace hasn't taken shots since he was in Brooklyn. He's had 4 and 6 FG attempts in the last two games, which, yes, is amazingly above his average, but hardly just pulling the trigger because Crawford is gone.
Probably has to do with starting, rhythm and routine (as he had recently complained about).
I don't get your point. Crawford obviously doesn't
directly affect how many shots Wallace takes, but without him and Bradley there's many more shots to go around (twice as many on some nights). I don't think I can explain it simpler than that.
Also I don't see how last year's Nets relate to the Celtics at all. They had 3 elite scorers in Lopez, Johnson, and Williams, plus another excellent one in Blatche. They almost exclusively played pick/roll or isolation, and hardly anyone took shots outside those 4. These Celtics are the complete opposite with no go-to guys, constant ball movement, and scoring by commitee. Wallace without a doubt SHOULD be taking more shots than last year.