Since Legion, Blizz has been trying to add complex systems to the game that will last for an expansion and then throw it away.
This somehow worked for Legion as the Artifact system wasn't that complicated tbh.
But was a nightmare in BfA, we had the initial system, a new system in the first patch, a third system in the second patch, then there was the cloak at the end.
These systems over complicate the game, and delay it in a lot of ways, tuning them is another story.
Why can't we have an expansion like Wrath or BC or even Cata? they didn't have much complicated systems, yet they had more zones, raids, dungeons, the story was even better!