that's not an accurate representation of Jane Foster, her Thor stories were some of the best in years. Jason Aaron did a fantastic job with her, the change was organic thanks to Original Sin and she was a fully fleshed character with realistic motivations.
Comics have to change or else they'd be horribly repetitive. I also find most of the people that bitch about supposed catering to a certain crowd aren't long time comic fans, bc long time fans know these characters change and evolve and new people step in all the time.
was there an uproar when Jim Rhodes stepped in for Iron Man?
if it's done right, they can lead to fantastic stories. The Ms. Marvel run that started her character was fantastic. She didn't replace Carol Danvers, she just took up an older mantle as Carol was Captain Marvel by then. Same with Miles Morales, arguably the best character created in the past 10-15 years.
the RiRi Williams story was lacking, but she was totally different than Tony Stark, she's a teenage genius who is learning to become a hero while Stark was at one point comatose but now he's back.
these supposed SJW characters that are supposed replacements? Show me one where the original hero isn't also being featured in stories. Odinson never left, he just lost his hammer and has been featured in stories the entire time. Stark? Even being comatose, he had an A.I. that was basically him and most stories involved the hunt for him. Bruce Banner was killed but wasn't dead for more than a year. Carol Danvers never left, Peter Parker (616) never left, etc....
no one was replaced, New characters were introduced alongside.