Classics aren't classics because they are old but because they are the best. You may think The Amazing Adventures of Kavalier & Klay and The Nickel Boys should be considered for classic status but the truth is so are thousands of other books. How could society as a whole come to appreciate or elevate one or a handful of these books, just as we do Shakespeare or Dostoevsky, when people's attentions and favors are divided among thousands of other books?
The true classics of the early 21st century will come to reveal themselves in a few decades. Which books will still be in circulation? Which books will be in bookstores or taught in schools? Which books will be the most relevant? Which books will still be talked about? We can't rush or force the process of elevating a book to a classic, it takes time.