Give your opinion to why you think people burnout
A lot of assumptions and only my personal opinion:
1- The Fun of the game comes from numbers
Item level is a big part of the game and for some is the "whole game". The problem is once you reach your skill cap, be it Mythic dungeons, Normal mode or Mythic mode, the game ends because you reach your max item level available for your "skill cap".
Meaning people stop playing once they reach the max item level available for the max difficulty they intend to do.
2-Combat Gameplay is not necessarily Engaging/Fun
It's a tab-targeting oldschool MMORPG meaning all the fun comes from "DPS/Healing/Tank rotations" and "Damage Meters"
It's not an action game like many other modern multiplayer games with cool animations, interactions, combos, reaction based and mechanically intense gameplay.
It's just an opinon and an assumption that this type of oldschool MMORPG playstyle is not "fun" on the long term and is easily overshadowed by other modern multiplayer games.
3-Repetitive Nature
This is not necessarily bad because all games are repetitive but this on top of "not engaging combat gameplay" is the perfect mixture for fast burnout.
We repeat the same content over and over for hopes of "better numbers" (item level) that doesn't open any kind of new gameplay when unlocked.
It just makes us better equiped to repeat the same content again.
4-Lack of Server community Interactive Gameplay/Competition
The only "server community gameplay" in the game comes from "World Bosses" (they are not exactly engaging) and competition to see which Guild is able to kill Mythic Guldan first.
When we are in a community we want to be competitive and interact with a group of people.
Lack of leaderboards of DPS, activities to conquer places and be competetive with one another makes the people feel disconected to the world and feel...kinda alone if they don't have anything to compete with and be known on the server.
I think more activities to be known on the server would be an excellent addition to the game.