I'd say we need to get Giannis if Brad wants to retain Joe and his lengthy contract. Having Giannis means that Joe must modify his offensive philosophy to suit Giannis's strength, which will lead to a reduction of the 3pt attempt, hence more efficient offense.
However, if we can't get Giannis then Joe still has to modify his offensive philosophy since it doesn't fit our personnel. We no longer have Jrue, KP, All (all were efficient shooters) and White, Hauser regressed. Joe needs to fit his offensive philosophy to his players capability, not the other way around.
The last option is to fire him.