Immortal/undying title, amani war bear, sinestra achievement, mounts getting reduced to 1% drop rate in new xpac, challenge modes scaling gear down etc...
It's not ideal, but pve still gets some things left for the elite. Why shouldn't these sets be the same?
The removal of the Immortal and Undying titles are poor examples because Blizzard has changed its policy since that time. No other achievement based title, or any other similar reward for that matter, has been removed from the game since that time. And they were hardly marks of "skill" even when they were relevant, because even normal mode Ulduar gear trivialized getting them due to how easy Naxx was.
The Amani War Bear is now available on the Black Market Auction House, as are all those mounts you mentioned that have been dropped to 1% chance. If you advocate keeping this "exclusive skill-based" reward in its current form, then I demand that you advocate the addition of every season's Gladiator drake to the BMAH. If you don't you are a self-serving hypocrite whose arguments have no merit.
Challenge Mode Dungeons use of gear scaling means that even when we are level 100 in ilvl 1000 gear, they will be just as difficult as they are today. Challenge Mode armor as a "trophy," which you claim the Elite PVP armor is as well, will still be relevant no matter how far in the future we get. High-level PVP functions in exactly the same way as a self-check on difficulty with a permanent curve. If you advocate that Challenge armor is an "elite reward" that should be left as it is now, then I demand that you advocate the return of all old Elite PVP armors to the game with intact rating requirements for their purchase. If you don't you are a self-serving hypocrite whose arguments have no merit.
I doubt you will agree to either of these demands, because like everyone else who argues for "exclusivity" being a good thing, you are an egomaniac who has a compulsive need to prove you are better than other people at a videogame, and its much easier to do that by resting on the laurels of a past accomplishment and excluding others from that accomplishment than by constantly maintaining relevance on the current bleeding edge.
Have a pleasant day.