The answer is yes to all the above.

Yes we have seen the Captain America role change many times, and each time, as fans, we might even believe the change is meant to stay. Fans get all bent out of shape, and things go back to normal in a few issues. Why? Because it's only a story.

Yes we justified in criticizing, or I'd rather say, have an opinion, of the current stories, but its a bigger yes that most on this board have seen the same stories time after time. That is just the way it has to be when you have so many titles told for so many years. There are only so many stories to tell after all.

Yes the casting is politically motivated to push Falcon, a black hero, to the forefront. Odds are Marvel is trying to get a movie or show started with him in the lead. 

So in the end, there are a couple factors that everyone has to internalize. 

We HAVE outgrown comics. We want to recapture our youth but can't, and blame the comic publishers for out inability.

Change is painful but inevitable, but we can't get over ourselves.

Yes, internet opinions have illustrated how extreme people can be when there is no filter. 90% of the moaners have forgotten or ignore common rules of etiquette. Most trolls are simply cowards.

The newer generations actually believe they are entitled to make demands of comic publishers, as if they were true business investors, whereas the roles of paying customer and corporate investor are completely different.

On a side note, I did check out the female Thor because of all the changes in recent times, thats the one that irked me. Once I saw that it was not some stupid gender bend trick, I was fine. (I assume it wasn't a gender bend trick, but I didn't read the book where she actually picked up the hammer)

And for Brevoort's role and reputation, anyone who has ever worked in a corporation at a management level knows you have to tow the corporate line, with no deviation. Some people get stuck in roles of damage control and must suffer the flak, some get stuck in roles where towing the line conflicts with personal belief, but who can risk leaving their job every time our job gets uncomfortable?

The problem seems to end at the border, though.  I can't say I've run into the opacity problem with (say) Japanese manga, so I'm pointing the finger squarely at Big Two books as they are now.  A good Japanese book like Death Note is both way deeper and way clearer than any new Big Two book I've picked up in possibly decades.

I think there's a good reason why serial Manga translate well into serial Anime:  Solid story-telling.  I actually did start the Death Note anime in the middle, before realizing it was so good I had to start from the beginning and go buy the books (which the Anime follows admirably).