Firstly because its impossible to escape the fact that these changes are agenda driven rather than story driven.
Secondly because all of my favourite characters have been marginalised in someway, and until that changes they ARE ruined.
Finally because what they have been replaced with for the most part pales in comparison.
I'm dropping books left, right and centre, and thats got nothing to do with the fact that my favourites have been replaced - because I count numerous replacement heroes including John Walker, Jim Rhodes, Eric Masterson, and Carlos Cruz amongst my very favourite heroes of all time
Firstly its because the originals werent turned into villains, or killed off, or disgraced when those replacements were brought in as an effort to legitimise the characters talking over from them.
Secondly its because stories like 'The Captain', 'Demon in a bottle', 'War Machine', 'Countdown' etc were excellent stories that made the change appear entirely organic.
Finally its because what they have been replaced with is for the most part incredibly dull.
Legacy is giving me the opportunity to jump off an additional half a dozen titles, because I'm sick of letting myself down paying for sub-par material filled with political grandstanding and more interested in trying to appease the mainstream media with how cool, hip, and diverse it is, than just telling a solid story.
The main difference too is that whilst I think it was always accepted that those earlier heroes were going to be temporary replacements, theres no doubt that these new heroes are here to stay, and no matter who they are the core concept of Cap, Ironman, spidey, Wolverine etc are all made ridiculous and diluted by having half a dozen people running around claiming the name at the same time.
I don't see how this is going on any more than usual. Remember Jim Rhodes and John Stewart (This is before Spawn.)?
And again, characters change back all the time. In no way are most characters permanently ruined. Do you think that people didn't say the same thing with those stories that you mentioned, or when Tony became an alcoholic? Or,heck, when Peter and Mary Jane got married? Of course there were, but there was no internet then (Al Gore didn't get around to inventing it.).