This is what the whole 800mm gets me out of the RF 200-800.
To the astonishment of people who have never tried to take a picture straight at the moon before, this is only a 1/800 sec exposure at ISO-100. The normal rules about nighttime sky photography don't apply for the moon on a clear night, because it's lit by direct sunlight.
Are you using 1/800 to deal with the movement? I was surprised by how much it moves when I took an astronomy class in college. When I worked in TV at some points I controlled a camera on our tower and if the weather folks wanted a big image of the moon I’d constantly have to adjust the aim right up until it was on air.
Personally I like the exposure on the moon to be a little brighter so I’d probably bump the ISO up a little if it needs the fast shutter, or the aperture if it can open up any more. Nothing wrong with your photo, of course, just a personal preference.