I have heard the different cruise lines cater to various demographics - Would like to know the good ones.....
That's correct, each line is after a "Certain Target" the cheaper the cabin the more interesting the people will be.
then theres some luxury cruises
https://www.oceaniacruises.com/default.aspx they are expensive but we are talking about the difference between driving a Yugo and a Porsche, from ports of call to service the difference is day and night, BUT a cabin will cost you around $700 @ person per night versus the regular cruise for a "closet" I mean inside cabin which will be $80-$100@night per person.
Believe it or not theres a lot of happy people with the cheaper cruises but then again theres a market for everyone.