Classical music does not just mean symphonies and orchestras.
It was a term coined specifically to refer to that type of music, created before the rise of the music industry i.e, before recording.
It was done by... snobs, who were less than trilled about different types of music taking becoming popular with people. Especially sine music like Blues and Jazz have roots in American folk music. So, the common people were deciding the popularity of music, instead of former taste makers.
So, it has more to do with when, not what.
Think of it like this, there is no new classic rock. The term specifically refers to music from the 50s-70s. Not even necessarily the 50s, or all of the 70s.
The 80s and 90s are further from now than that classic rock era was when the term was coined, but people are not rushing to call music form those decades classic rock.
There are two interesting elements to this...
1) It proved that those snobs were ultimately wrong. At the time classic music was being produced they looked down on folk music as being lesser, and and it being far more influential with it often being tied to cultural studies.
Also, because Blues not only came from folk music, but was one of those early music types they wanted to brand as lesser, and became the most influential music ever.
It spawned R & B, and Rock music. Adding more blues in varying forms gave us the Rolling Stones, and psychedelic, both of which were influences on early punk bands like MC5 and the Stooges, as well as early Metal like Steppen Wolf and Black Sabbath,
Blues was also the roots of funk, which is what led to rap.
Also country music came form folk music, which means that that the very music they thought as lesser became the most versatile and dominant form of music ever, through its decedents.
2) that similar versions of that type of gatekeeping would keep happening over time, in various degrees.
Some of it was generational, with Greatest generation jazz nuts hating rock, those same baby boomers who defended rock hating their kids and rap, or pre-war jazz fans having contempt for the likes of Miles Davis and Coltrane and visa versa (look up the jazz term 'moldy fig')
Other far more sinister As Bob Dylan once pointed out, in the early 60s as rock n roll became established through white musicians, many record store owners did weird stuff. Namely, having music that was very similar being designated as Rock n' Roll if the artist was white and R & B if they were black.
The very idea of classical music is the grandfather of every music snob, parent telling their kid to turn down the racket, race based music marketing and blocking, and high school clique defined by the type of music they listened to
So, is classical music dead?
It is more like the old rich curmudgeon on the hill that never leaves their home, and dislikes their kids and grand kids for mixing with the new money and less well-off.