One of the OP's premises he uses to construct his argument is flawed:
"As the history of the Beatles begins to become akin to Tchaikovsky and Mozart, we need to be introspective.
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It's easy to say that good music will live forever, but does anyone *really* know everything by Beethoven by heart?"
In fact, fandom of various classical greats (the ones mentioned above and many more) remains thriving. Think of all the symphony orchestras and chamber music groups continuing to perform their music in every city of the world; think of the societies, associations, and schools and colleges funding and promoting their ...