It is ultimately the job of the editors to balance to balance fan expectations and the needs of the story. And the editors were the ones who failed to do that. My father liked to tell of how at a convention in the 70s he suggested to Stan Lee that characters like Mr. Fantastic should age in real time since Marvel was trying to be more realistic than DC and Stan immediately dismissed the idea and told him that Marvel time worked differently. My father wasn't resentful. He was just glad to meet Stan Lee.
When it comes to nostalgia I'm in a weird place because the comics I find to be the best were all written before I was born. I grew up reading my father's collection of old Marvel comics from the 80s, not just X-Men but Iron Man, Avengers, Spider-Man, Fantastic 4, ect. And even as a little kid in the early 2000s I couldn't but wonder at how these old comics were so much better than anything Marvel seemed to be putting out for any of those franchises at the time. It's why I stopped getting comics at all in my teens. Why spend money on an inferior product when I could just read better books for free?
I often hear about nostalgia for the way things were when you were a kid, but I'd actually hate to have the Marvel of my childhood back. My 'nostalgia' is for a period before I was born. But no golden age can last forever. I do find it fascinating to try to examine what worked then and how the decline occurred. There was a ton of behind the scenes BS that was outside the writers' control.