Have Marvel comics changed for the better or worse?

[Probably_not_a_Nurgling]

And you're still ignoring subjectivity.

The fan in my movie example is a "new" fan...so, again, would their irritation be valid if Iron Man 3 (in continuity with Iron Man 1 and 2) ignored or reversed vast portions of the previous movies?

If a book comes out that completely ignores or reverses something you like and it upsets you, will your own feelings be valid at that point?

Yes, that would be valid. It's happened to me. I'm not saying feeling that way isn't valid. What isn't valid is arguing, as you seem to be, that comics were objectively better at one period of time than another. For example, I found the dialogue in Secret Wars painfully outdated. Does that make me a "bad fan?"