I could be really wrong on this, but I believe that most (if not all) music genres are derived somehow or other from classical.
In other words, my personal favorite (rock) wouldn't even be around if classical hadn't been here first. So maybe the same number of people don't listen to classical as listen to Justin Beiper, but classical is still very relevant. Other genres are built off of it, influenced by it. This sounds corny, but it's a bit infused into society around us. If you ride an elevator, chances are it will play you classical music. If you are put on hold by a professional company, chances are they will play you classical music. There is at least one radio station in nearly every city I've lived in devoted only to classical.
I.. I don't think anyone here is saying that it's not relevant. I think that Cuelebra is trying to say that the hordes and masses prefer other things because they are a bunch of doofs who have the freedom to like god-awful music if they want to. But classical will always, always be relevant. That's why it's "classic." If I've misunderstood the whole thing, then please forgive me. D: