Marv Wolfman believed Peter should never have left high school during his run...and that was well before the wedding. Stan Lee commissioned the story that became the first clone saga as a possible backdoor for Gwen's return...(had the Peter/MJ romance not been popular, that would have been it, Gwen would have come back right away). Fact is there had always been changes in Spider-Man before then and people didn't like those changes or saw it was best. The marriage, and the way it happened and so on polarized writers and editors, and radicalized those convictions.
There's also the fact that retcons and ideas like that in Marvel and DC became more common in other comics and continuities. X-Men undid the Dark Phoenix Saga and brought Jean Grey alive. Jean Grey's death was a "Gwen Stacy moment" in X-Men continuity. But not even ten years away, they retconned and undid it. They said that the Phoenix in that story wasn't Jean Grey. It was Kurt Buseik who came up with that. He was a fan who didn't like the Dark Phoenix and felt it ruined the story (as this fan letter he wrote confirmed:
https://imgur.com/xrWq7Of). Buseik is another of those fanatics who believe Peter should never have left high school. So you had bad practices coming in as Silver Age nostalgics and so on became set and hardened against changes, vampirically sucking at the new in favor of the old.
After seeing COIE and the Post-Crisis Superman, the Death of Superman and so on, and Jean Grey's resurrection, that may well have led Spider-Man writers to go, if them, why not us. But Spider-Man did hold out for a fair bit longer than others.