Considering a chunk of this movie consists of flashbacks of how Carol Danvers "becomes" a super hero [spoiler: her super hero name doesn't show up until the end] the actual story is quite short.
In the comic books Captain Marvel was actually a male. I am guessing those at marvel enterprises decided that they needed another female super hero - which is fine. I was never into comic books but I wonder how some enthusiasts like the change. Some I'm sure do [was it her looks?] and some don't.
On a side note, interesting the Captain Marvel has the same last name as Supergirl. Related?