That might have spoiled one of the biggest tellers of the plot.
One of the least surprising cameos, although still pleasant, of Captain Marvel was the brief, percussive appearance of Ronan the accuser. Ronan does not do much, but his appearance as the first accuser of the Kree empire has created a sense of continuity with Guardians of the Galaxy and makes the cosmic side of the MCU more coherent. Besides, he's just a nice guy. Beautiful shade of blue.
As stated in the Director's commentary for Captain Marvel, The filmmakers deliberately limited the scope of his appearance and decided not to present it until the end of the film for a simple reason: to present it early could have made the comic fans forget about the big turn of the film.
You see, in the movie, the Kree are, well, they're the bad guys. Here are the relevant quotes transcribed by CinemaBlend:
Anna Boden: Here we have the Accused ships that are the Kree anti-bomb squad. So we've already met Starforce, which looks like the SEAL Team Six, and we're now seeing the bomber group bombing a Skrull fortress in the south. We played a lot with the question of when we present Ronan in this movie. Should we present it at the beginning of the film as the main accuser of these Accusers ships or should we keep this information until later?
Ryan Fleck: Yeah, I think it was more effective to hold on because it was too early because the Kree were the bad guys because everyone associated them with the Guardians of the Galaxy and it really gave way too much early.
Boden and Fleck were worried, I think rightly, that casual viewers would get the quick hint that Ronan = Villain and assemble that the Kree Empire was not a heroic. But are there really heroic empires?