PvP gearing worked fine in BfA, with scaling to reduce the power differential. But too many elite players complained that they couldn’t delete casuals any more, so Blizz took it away again. And also in BfA we had TF and, again, many elite players complained about casuals having too much ilvl, so Blizz took that away too. And look at Corruption - here was a gear system where ilvl became a lot less important… and many end-game players absolutely hated it (I know the RNG element was part of this complaint, but there were also plenty of complaints about how some lower level items were doing much more damage than higher ilvl items in a player’s inventory).
The moral of the story is that in WoW, increased player power = character progression. For many end-game players, becoming A LOT more powerful over the length of a patch is the main motivation for re-running end-game content. Not just to push higher keys or Mythic raid, but to flex and show they’re better at the game than casuals.