Well, from an in-universe perspective, Carol's original costume (In the first issue of her own series up there) was actually created by her subconscious mind to emulate a female Kree officer's uniform.
Okey, it's a long story. Originally the schtick with Ms. Marvel was that the psyche-magnetron which gave her her superpowers fractured her psyche into two distinct personalities. There was Carol, the down-to-earth, normal career woman and Ms. Marvel the Kree superheroine. Neither side had any idea they were the same person until a good while into the series' run.
(Heck, Carol's warrior persona had the short hairbob, while civilian Carol had long flowing hair. Kree shapeshifting, ladies and gentlemen)
Anyway, as soon as Carol's personalities started to integrate she also changed her costume, first to a full leotard version (eliminating the big tummy cut-out) and then to her black-with-thunderbolt suit.
So while the Kree are arguably the sexist ones here, Carol's not to blame since she was just emulating their dresscode.
Now, from a REAL WORLD perspective... there's not really any excuse except "It's comics" and "it was the 70's".