I’m no fan of the family pool. I agree with everyone else that it’s way too small to be enjoyable, especially on a sea day.
But otherwise, while there are lines for some stuff on the ships, and there are choke points for foot-traffic flow, I have never thought that a ship felt “crowded”.
What lines there are, are relatively short compared to many of the lines you wait in at WDW. You are usually in shade or air-conditioning, too.