This is the kind of topic that must be publish on the council forums when they’re up, the own developers created this FOMO situation, because systems and gameplay were designed to be discarded, some FOMO items like gladiators, m+ for my perspective is OK because is something that measure your skill in that point of time, however Challenge Mode and Mage Tower were good gameplay systems discarded instead of becoming something to look back for new and old players.
That’s why they’re removing borrow powers from the mage tower now, at the end the playerbase doesn´t have a big voice because they brough items that you considered “rares” “no longer available” to the BMAH, or change achievements to be easier like mecha-done, Devs can change anything at any moment.
The idea of glorify something in game depends on the reward and system that provided it, at the end , the best thing for WoW is to keep as many rewards as possible in game, no matter the expansion and the gameplay should trascend one single expansion, otherwise the game will keep bledding players.