Its moral is that no matter how tough you think you are there's always someone you answer to and that you ultimately will, indeed, if you screw things up.
In fact, in my opinion, it's one of the best organized crime movies of all time. Casino is one of the best movies of the 90's. You have to be objective when judging this movie and those of us who criticize everything that stands out amongst the grey background of that which is mediocre are fools who envy others' accomplishments and view them as insults to their own personal uselessness. This film speaks even to those who dislike the subject of organized crime.
Casino is in my opinion an epic, but it's much more than that. Watch Casino with a subscription on Peacock, rent on Amazon Prime Video, Apple TV, Vudu, or buy on Amazon Prime Video, Apple TV, Vudu. Martin Scorcese's harsh and yet delicately balanced masterpiece rises above anything petty meaning that if one wishes and has the ability and means to create a Sicilian mafia movie he should do so with grandeur and put into it as much effort as possible for people remember those who take advantage of their talent and circumstances and are diligent in their undertakings.