I don't think it's bad. I think it's great for continental grips which contact the ball beside the body with an open racquet face. Like I said, I know a few high level players who use it for that grip.Why do you think closed stance is so bad? Do you have a video of you hitting?
For a modern grip, you don't use it to rally.
It isn't about what I think. It's like asking why I don't like peanut butter and mustard sandwiches.
Both are great in the correct context. But never together.