Yeah, it's not about the GOP.
It's about the Democrats moving so far to the left they are losing centrists.
There are very few Democrats who could credibly change parties to the GOP given their stances on social issues. But they can change to independent and still remain fiscal conservatives and social liberals. That's what we used to call centrists or moderates in both parties.
By the same token, there are very few Republicans who could change to being Democrat. Maybe Romney and Murkowski. I could see both of them also declaring as Independent.