Please explain Classic+

I was unfamiliar with Classic+ until I came cross many posts recently. So I looked it up on Google and from what I understood, it's mostly based on rumors and words of mouth. Am I wrong so far ?

Also my biggest interrogation regarding Classic+ is this : people suggest that instead of new expansions, Blizz releases new content for Classic ? Isn't that...what defines an expansion ?

I mean, people love Classic because it's classic, it's what they are used to. Why changing it, when it's also the best way to make people say "they ruined Classic, old Classic is better" and all of that.

I'm really confused about this Classic+ hype, to me it seems that some people want things to change and to stay the same at the same time.

But please, correct me if I'm wrong, I'm genuinely confused !