I loved it in winter. Went in Nov/Dec. 2020
No real crowds, smooth traffic, 1/2 full parking lots.
Still plenty of people but nothing crazy.
Only positive comments on the bus from park staff and other campers.
Mine is only 22' long, so I didn't even rub up on the guard rails.
I compared this experience with extended family from a summer trip they had in a mini-van the previous summer..
Big crowds, Grid-lock traffic, parking lots full to overflowing, hard to find a camping spot...
That was previous to Covid, so your experience may vary.
We hit the Grand Canyon on the same winter trip with similar results.. Even less people camping at the Canyon... Off season is my season.