The idea that Smart is the problem makes little sense to me. Let's see.
Assists: 1st
Assist/Turnover Ratio: 1st
Steals: 1st
Free throw rate: 2nd (after TT, a center)
TS: 56%
His shooting comes out to right around league average, with this high free throw rate (where he shoots 80%) and taking most of his shots from deep while shooting a respectable 35% (same as Kemba and Devin Booker this year).
Meanwhile, he's top of the team in assists and steals, he defends multiple positions well, he plays hard, he protects the basketball.
Having 3-4 players regularly in the rotation that basically don't contribute on offense is an issue. Tatum taking nights off and shooting 49% (same as Smart) inside the arc... problem. Kemba being a shell of himself. Fournier being a complete zero in half of his games so far. No depth. Etc etc
If Smart leaves one day, man is this team going to miss him.