There's no reason to change these characters beyond nostalgia.
This is my personal opinion, but nostalgia can easily become a poison. It's this poison that leads to creators bending over backwards to cater to guys that remember how "good" things were when Peter Parker was single or how Barry Allen was the Flash and he must be "the only Flash", decades of successful storytelling be damned. American superhero comics have gotten weird because they are now stuck in a loop, the illusion of change can only go on for so long without permanent consequences. There's no other storytelling medium that features largely unbroken storytelling like American superhero comics, the older characters are almost at 100 years of unbroken stories (the so-called reboots almost always bring back pre-reboot elements and nothing ultimately changes) and the cracks are getting harder to fill with the "illusion of change". The medium has lasted this long because there were points in time when permanent changes were made (like how silver age characters were replaced without looking back, stuff like All-New X-men etc), constantly going back to how things were isn't helping the industry or its fans. Even as an individual, constantly looking back to how good things were without fully embracing where one is in life, how the world around one has changed and how to move forward is a recipe for misery. If something or (or even someone we love) has changed too much, you have to consider how you're going to approach them or even let them go. Again, these are just my views though.
There's nothing wrong for liking Carol as Ms Marvel but how does her going back to Ms Marvel improve her current standing? Kamala is a fairly successful character that people have seen on tv, games and very soon a movie, why change the character's identity?