Carnival, like most cruise lines and other businesses, are having staffing shortages. I was on the Ecstasy last week and experienced lines and slow service at all food venues, but not as bad as what you mention (10-20 min at most locations unless peak times). I think this will continue to be an issue for a while.
The cruise lines need to get back to full passenger capacity to make money, but that may be a mistake in the long run if passengers are disappointed in the onboard experience and decide not to return in the future.