First, there are many stories/IPs that are so fucking overhyped and insanely regarded that it doesn't matter how good they 'objectively' are. The first Star Wars movies don't deserve the psychotic hype which transformed it into a commercial industry supporting cities of human being's livelihoods because NO FUCKING STORY would deserve that hype, but here we are. Compare this to the bible stories (which are objectively shit boring stories mostly due to redactions and later editing) or the Iliad and Odyssey, or Gilgamesh, or Romance of the Three Kingdoms, Journey to the West, Shakespeare or Don Quixote. 1001 Nights. These stories survive the test of time naturally or through religious/cultural mandate. There were probably many stories lost that were once required to know for citizens of this or that lost empire.
But now we have 'free markets' and 'free speech', so we can't really know, for example. If the Beatles 'deserved' the hype (no one really does, that amount of hype is delusional and dangerous - no one could even hear anything during Beatlemania era concerts due to the audience screaming their heads off, hyperventilating and ending up in hospitals) due to their talents or due to the marketing and the commercial response. It's a chicken and egg problem. Is Harry Potter a good story, or did it stimulate a global commercial machine on it's merits or on accident? Why didn't similar children's books do the same thing five years before or ever since? Is it really because Rowling is a genius?
You can't really 'trust' what's popular now, it has to pass through the test of time, but even this only transforms stories from 'unimportant' culturally to 'important'. It doesn't say if these stories are good or valuable in any other sense.
In general, there is a good reason to doubt if something is good or not and opposing the mindless popular opinion is necessary to see if these overhyped products aren't in fact dangerous or worthless.