No to the basic question for any individual sailing.
You can have an idea based on season. School breaks = families traveling with kids. Lots of kids. Off-season has more couples or people with pre-school/ younger kids. Panama Canal cruises are often less crowded, though possibly sold out.
Short cruises, weekends, and new ships, Summer and Holidays are more full.
(Unlike a trip to WDW, a crowded ship does not mean you spend most of your time in a line!)