I think we hit a better point in BC/Wrath, and gradually gutted it. Outside of raids, your spellbook was bigger and more useful in a situational sense. Anymore we just get half a dozen ways to AOE things, and the single target rotation is about the only interesting thing left.
Your other criticisms of vanilla are valid, though people who enjoy it more than BFA aren’t blind to the warts. They just think the sum experience is better.
No, Rustbolt gives you a near-bis trinket, one that’s so powerful it’s near-bis for every spec in the game, and it’s the exception that proves the rule because it’s the only rep gear in the xpac that isn’t utter trash. Everything else gives you horses and 355 items that were terrible by the time you could buy them and weren’t even functional for mogs because they were almost all identical recolors of the same two slots. Best case they’d give you a minor efficiency upgrade of a recipe you bought from the trainer before you hit 120, and you’d usually still have to get the R3 somewhere else.