That's a terrible idea for a few reasons, but one of them is that a conventional automatic transmission is designed for the engine to be turning at idle speed or greater all of the time. That means that the motor will pointlessly spin even when the car is not moving, using power and producing nothing useful.
When people converting vehicles to EVs use an automatic, they significantly modify the transmission to make it workable. For most applications, this is a needlessly expensive and complex approach.
