Superman can shake the boat but not that reputation I guess. He's had as many long term dramatic shifts as any character but is still deemed safe. He is considered stodgy even though three of the last four films have gotten knocked for radical developments and departures from what people know. Who knows for sure but I think the controversy of Jason white was only just masked by the Donner coating.
If it took until the mid or late 80s to realize Superman's low mileage, I think people were pretty generous. Superman was hardly ever toyetic and as comic sales could never have lasted forever, the writing was on the wall.