Earlier quoted context omitted.
Your confusion is completely right. The genre classical has an almost insanely wide meaning. It originally only meant music from the Classical Period of 1720 to 1820, then Romantic music after that, and thus everything you describe above ought to be termed contemporary music (and is usually called something like that as a sub-genre). There is a marketing explanation which is often the easiest definition to use, which…
> Your confusion is completely right. The genre classical has an almost insanely wide meaning. To pundits, not to the common man, for which it means "mostly artsy stuff done with acoustic instruments by conservatory trained composers and performed and their like". Heck, for the common man even the distinction "classical", "romantic" etc doesn't mean anything, Bach and Mahler is all classical, and even for my brother…
It's actually about lineage. Contemporary classical sells itself on the basis that there's a direct academic - sometimes historical - link to Beethoven, who was the prototypical Genius Composer.
Which is why you usually get all the stock tropes - concert halls, serious audiences in seats listening very intently, serious clothes for the players, a serious conductor at the front, clapping at the end only, definitely no cheering or dancing - that also apply to traditional classical music concerts.
It's also about intellectual content. Pop doesn't usually try to justify itself intellectually. Contemporary classical does nothing but. Which is why it's a long series of "isms" of various kinds, all making more or less convincing claims about their own immense cultural importance.
You don't get points for writing interesting music, you get points for creating a new "ism" - preferably an "important" one - and then writing music around it.
The committed audience is actually tiny - five figures globally, if that - so "important" is debatable.
Even so - the idea that contemporary classical is "important", with the implication that other music isn't, is probably the key to the genre.