do you have LoD and RS25hc on all 10 classes, all 27 raid specs?
are you the best player of your class in each 25man hc raid?
theres always new things to practice and learn, we just play this iteration of the game because its the most enjoyable version for us.
i have friends that come to wow for 1 month to kill the Lich King on 10man normal and think they have completed the game, meanwhile they are completely clueless that they just got boosted in a 9man icc that i had to bring a bis char just to get them invited xD
killing LK isnt the endgame, we killed that guy 14 years ago.
if you dont enjoy repeating content then a static patch private server probably isnt for you, maybe try the new Onyxia realm?
i personally dont like progressive content anymore because it feels like a full time job to keep up with the progression, and if you take a break you fall behind.
on icecrown i can take a break for a year and come back to pick up where i left off.
at a certain point pve just becomes pvp, playing vs other players on the dps meters