I assume this is about the Canon[1] thing? And who gets to be the Gatekeepers - the people who decide which writers and works get included and excluded in each generation's version of the Literary/Musical/Artistic Canon thing?
As far as I can work out, it's mainly about what stuff the professors and teachers teach to the students and kids as part of their formal education. Whoever gets to set the curriculum also gets to tweak the Canon? Outside of formal education, things get a lot more fluid and fun: Canons take decades to change; Cultural tastes can evolve over weeks.
As for Shakespeare, he wasn't considered the English language's greatest writer during his lifetime, or even after (according to Wikipedia[2]). It took him near 200 years to gain such acclaim.
[1] - https://en.wikipedia.org/wiki/Western_canon
[2] - https://en.wikipedia.org/wiki/William_Shakespeare#Critical_r...