My family likes cruises and we use to sail on Carnival, but are branching out now that they changed their loyalty system. After experiencing other cruise lines I can definitely say my opinion is it's just the clientele, especially on their shorter (cheaper) cruises and depending on where you sail out of. We did a short cruise on Carnival out of Galveston a few years ago and the people were terrible. Last year we did a short cruise on MSC out of Port Canaveral and it was completely different and was a great experience.
I also hate Carnival's 15 per day drink limit. Not that I hit that limit a ton, but I don't like counting my drinks on vacation. But it's interesting that they are one of the only cruise lines with that limit and they still have all these problems. Royal has no limit and MSC has a 15 drink limit with their package but you can buy more after that, so no actual limit. Yet, you don't hear about them having the drunken problems that Carnival does.