I really couldn't see anyone who is a fan of the modern direction to love Vanilla again. The games are so fundamentally different.
To me Vanilla was more about game design that incentivized socialization and making a believable world.
I cant stand modern design that is all about fluidity and pacing. That makes the whole world feel fake and plastic, and I consider it bad game design in turn.
In all things that matters Classic is a better MMO, and a RPG.
Somewhere among the stars is an MMO that has modern game design, quality of life features, quest diversity, multiple paths of endgame progression, compelling boss encounters, varied and balanced class specs, as well as a world the encourages communication with others in a living world.
Retail and Classic have aspects of what I want in an MMO, but they're two incomplete halves. While I enjoy retail more, I do want some of Classic's game design philosophy added in.
And I honestly think that Classic feels plastic. No NPCs act like characters. They're given no storylines or character development; they just stand in one place. The "towns" are 2-3 buildings tops, I'm given context to quests but it doesn't feel like a story; they're just tasks, and the world doesn't react to anything I do. Bethesda RPGs have more life to their worlds.