We've done so-called luxury lines and been underwhelmed (Crystal, Silversea). All-inclusive just meant mediocre wines for free, and the butlers were indistinguishable from cabin stewards (we never have any special requests). The sea day lectures tended towards idiotic.
Admittedly we've always been in the Grills on Cunard, but that offers the closest to a truly luxurious cruise experience we've found, given everything else available to see or do on board those beautiful ships. We have a Seabourn cruise coming up in December (totally itinerary driven) and I expect it to be comfortable; but given the relatively low cost of the cruise fares I don't expect it to be luxurious, at least according to my understanding of the word.