It is absolutely dangerous to try to have the perfect ship for every type of guest. No cruise line has that and no cruise line wants that to have. Because it is extremely difficult to offer a good service all these different types of passengers. So it is much easier to concentrate on a specific type of passenger. Of course the cruise lines try to get as many different passenger types as possible onto their ships, but not at any price. NCL has 2000 Passenger ships, 3300 passengers ships, and 4000 and in future 5000 passenger ships.
If people want to have smaller ships they can go to Oceania or regent. If they want to have expedition ships, there are other cruise lines available on the market.