I have heard the term “Premium” applied to Disney, Celebrity, sometimes Princess or HAL.
(Mass-market lines would be Royal, Carnival, NCL, MSC in the US. P&O for the Brits. And they have the more basic companies, too, like Marella).
Luxury is a whole different ballgame: Regent Seven Seas, Oceania, Azamara.
Somehow, I think Viking and Cunard might get their own tier level. They fall between Premium and Luxury - still affordable to many. But the emphasis on formal might still be there. Almost think “adult,” without the need to make it sensual, like Viking.
My sister is preparing for Cunard in Alaska. Floor length gowns for Masquerade and Glacier Night. So different than our previous Disney and Princess cruises there. Sure, we wore dresses to dinner, but we still do that on most cruises - unless we run back to the ship just in time for dinner. That late night sunset can change how port days go.
I am probably preaching to the choir. But having fun thinking of the variety.
Disney is definitely a niche market, not quite as small as Paul Gauguin cruises or other most of us wouldn’t recognize.