I wasn’t born yet when the OT came out, but I do know that the fandom seemed to be a lot more unified in their love of Star Wars pre-TPM - even when the Special Editions came out in 1997. In virtually every promotional and news coverage video I’ve seen surrounding the SE’s and TPM before their release, the fans all seemed unanimously enthusiastic when in line to see the movies and when they walked out of the SE’s, regardless of the new additions. I feel like the period after TPM ended its theatrical run was the point when the fandom started to become divided into sects - OT vs PT fans, people who liked TPM vs people who didn’t.
I think the reason the fandom is so divided now is just because of sheer amount of Star Wars content that’s been released over the course of nearly half a century - none of it is all the same, there’s a lot of variety, which inevitably means some fans won’t like all of it. That’s true for ANY entertainment property that goes on for so long and produces that much varied content - some will simply just watch the movies/shows, read the books/comics and play the games they like and not do the same for the ones they don’t like, but there will always be fans who debate and argue over what products or aspects of the franchise they like and don’t like.