They let the problem go unchecked for too long to the point it compounded on itself after so many years to the point it's pretty much unable to be fixed.
"But there was / is no bias in racials people just totally chose their factions off cosmetic choices!"
The racial traits system needs to be removed from the game or relegated to cosmetic or out of combat abilities only.
- There's a reason that so many top PvP arena players are Humans.
- There's a reason so many top end PvE players are Trolls or Blood Elves.
At this point, the only way to get back to having an even split between the factions at the high end of game play is a choice between literally forcing factions upon people, over adjusting racials so Alliance racial traits become overpowered, or extremely incentivizing (not just trivial incentives like the extra warmode buff) for the Alliance players.
That aside, I don't think they care about the player balance, and will continue to just churn out mediocre expansions as long as people still play their game.
They had the perfect chance to do so in Shadowlands, but they balked. Factions could have been merged after the war and we could have moved into a new era of WoW where we moved to racial tensions and selections like picking a covenant or Aldor / Scryer for our conflicts between each other when it comes to PvP. For PvE, we could have all played together to "fight the big bad" since we essentially team up and do that anyway every single time a big bad crops up.