To be fair, Carol has had just as many, and most of the Marvels use multiple codenames. Monica was Captain Marvel, Pulsar, Photon and Spectrum. Carol's been Ms. Marvel, Binary, Warbird and Captain Marvel. Noh-Varr has been Protector, Marvel Boy, and Captain Marvel. Genis-Vell was Legacy, Captain Marvel, and Photon (he stole the latter two from Monica!). Phyla-Vell has been Captain Marvel and Martyr. The only ones with only one codename are Hulkling, Mar-Vell, and Kamala - and Teddy and Kamala have both been shown to become Captain Marvel in potential futures.
In fact, aren't both Genis and Phyla currently Captain Marvel too? Though the currently active Phyla is from an alternate universe where presumably Carol wasn't using the name. Genis though, he was resurrected, there's no reason why he couldn't have used the Photon name again like he had in the Thunderbolts run he was killed off in, except that they actually gave him a comic with the same naming structure as Monica's (Genis-Vell: Captain Marvel). The Photon name was vacant at the time (last year) as Monica was using the Spectrum name.