You do realize imports reduces GDP right? GDP = C + G + I - (Imports - Exports). That again doesn’t even count the impact of loss of wage base and tax base with lowering the money velocity, which also lowers GDP.
It would be more accurate to say imports are neutral to GDP. The increase in C (consumption) cancels the negative associated with imports.
But labor specialization does increase GDP in the long run and a society with high imports has high labor specialization.