Completely agree with you. IMO, cruisers are the worst possible people to determine what is luxury and what is not. So much is based upon our experiences. This reminds me of a discussion of caviar. Some people get so excited when they see "paddlefish eggs" on the menu (the cruise lines call it caviar which it might be to some but it certainly isn't to others.
What you said about service is true. Expectations are different depending upon the country you are from. Some passengers prefer to be treated and addressed formally while others would find it very "stuffy" and uncomfortable.
Also, I have learned that suite size is also subjective. While we prefer larger suites with 1 1/2 bathrooms, others are happy in a small suite (again, speaking only about luxury cruise lines).
The one area where we disagree somewhat is about being all-inclusive. Certainly, you cannot take a mainstream cruise line, make it all-inclusive and call it "luxury". However, when luxury cruise lines began going all-inclusive, the other luxury lines followed. In order to be AI and luxury, the food and service has to live up to the "luxury" rating.
Since 2004, almost all of our cruises have been on luxury cruise lines. We have seen changes. Luxury cruise lines are more inclusive (some cruise lines including air -- even Business Class--, excursions, etc. Also, the dress code has gone from formal to elegant casual. What has not changed is the level of service and food quality.
The bottom line for me is that, unless or until cruisers sail on all luxury, premium-plus and premium cruise lines, their input in terms of setting "standards" will be flawed. Actually, even if they met this criteria, who is to say that what one person considers luxury would be the same for someone else.
Luxury (6 star) cruise lines always must have somewhat gourmet food #1. Passenger capacity under 1,000. All suite or higher. and always white glove service.