Luxury is defined by public taste. You probably wouldn't find any in Titanic if you applied modern standards. But, 1912 weathy would find modern ships garish and lacking in taste. Both would be right or wrong depending upon the standards of the time. Personally, I miss the mini-skirt era. But, don't tell my wife.
Taste, as Captain David so aptly put it, is highly subjective. That said, the standards of today are very different from that of over a century ago. A lot of even the 1st Class cabins would not be legal today because of a lack of en suite bathroom facilities which even the humblest accommodation now is required to have.
Also in that day, a lot of the diversions and entertainments we take for granted today as fundamental either just weren't done and often as not, didn't even exist. Passengers were left to their own devices when it came to "social intercourse."
Big ships like Symphony of the Seas as impressive they may be, but does not always mean a highest standard class of luxury. Which the Olympic class ships were for.
I would of thought the rich want some thing on a smaller scale of the personal touch of service and not having to put with screaming kids running around with very little parent control this days!