I wouldn't process it that way, so I would not have that problem. The unprocessed version is fine. You're taking an OK photo and then trying to add light & detail where there isn't any.
No detail, but there is light. A purple background is much better than a black one.
BTW, with a color managed viewer and screen, the banding is visible.
I have more example I can post. Night scenes with blown highlights and noisy shadows taken at ISO 100, when multiple shots are not an option. What would be the best exposure then? I can see that 2+ stops would be enough.
My point is: the camera produced a technically fine image. You can't fault it for that. You didn't expose for the shadows and didn't need to. But in post, you decided the shadows were important after all, and you processed it in a way that created a problem for you.
I calibrate my monitor and I only begin to see the problem created by your post-processing when I turn the brightness all the way up to maximum (which I normally don't do). I'm reminded of a Henny Youngman joke ... A guy goes to a doctor and says, "Doctor, it hurts when I do this." The doctor replies, "Don't do this!!".
It seems like you expect the camera to have ideal dynamic range for any and every situation, and to tolerate any adjustment in post. But cameras/films have never done that and photographers have never expected them to. Perhaps some day that ideal camera will be invented. Until then, we make pictures with the equipment we have.
If a film photographer had tried to raise the black portions of an image, he would have discovered nothing but the haze of the film base. This problem would have been very well known to Ansel Adams. He tested and knew the abilities of his films and chemical formulas, and made amazing photos working within their limits.
So perhaps Nikon gives some extra room for lifting the shadows. Good to have when you need it. Perhaps Canon gives some extra room for pulling the highlights. Also good to have. Not a big deal either way, and neither prevents a photographer from making great photos.