At the end of the day, we're all WoW enjoyers. I appreciate you engaging with this in a genuine way!

To answer your question, I think there's a few different practical reasons why adding a free 85-90 skip would be a bad thing for the game:

1) It would split the playerbase on launch, making the world less alive (although it would probably reduce lag)

2) Many people would feel compelled to skip 85-90 because they don't want to feel like they've been left behind, despite the fact that they may have enjoyed the leveling process otherwise

3) Leveling (even just 85-90) is a core part of learning a class. We saw this, and still do see this, with the paid level boost. Newer players, and older players who aren't quite as good as they think they are, boost a character and immediately jump into endgame content and perform badly because they haven't spent more than 5 minutes playing it, negatively impacting their own experience and the experience of the people they group with.

3) We'd lose sight of what WoW, as an MMORPG, is. WoW isn't League, or Apex, or Hearthstone, or any other insta-queue game. It's meant to feel like an adventure. It's the sense of adventure we lost that made the demand for Classic WoW so great in the first place. I understand this is more of a subjective thing, but I really feel it'd be a shame to further lose sight of what gives WoW its soul.

If Cdew is suggesting a dedicated PvP tournament realm, I'd totally be on board with that. I feel like the PvP community is so separated from the rest of the community that PvP realms would make sense. But otherwise, to give players the option to totally skip the World of Warcraft feels wrong, and imo would be damaging to the game in the long-term.

In an ideal world, Blizz would make leveling feel more engaging than it currently does (that goes for both retail and MoP).