system
Given the following post, respond as if you're commenting on Reddit:
human
[Captain Marvel] Why didn't Captain Marvel do anything about Thanos before the events of Infinity War?

If you have seen Endgame, you will know that the reason why Captain Marvel hasn't been helping the Avengers is because "other planets don't have the Avengers."

Well, if she has been out helping other planets for decades, then why hasn't she heard about Thanos and attempted to stop him?  I mean, here is this strong, super intelligent being who's goal is to wipe out half of the universe, and he has been succeeding in that through the use of a near unstoppable army who's main purpose to quickly and efficiently wipe out half of the population of a planet.

Now, knowing what we know about MCU Thanos, we know that, chances are, he wouldn't just use his army once on 1 planet and say "wow, this is taking too long.  I'm just gonna wait until I have the Infinity Stones," so he has more than likely wiped out half of potentially hundred's of planet's populations, and yet Captain Marvel hasn't done anything about it?

Has there been any statement as to why Captain Marvel in the MCU hasn't done anything about Thanos?  Is there even an explanation in the comics for it?
gpt
There are billions upon billions of galaxies in the universe. 

Thor, an Asgardian charged with protecting the Nine Realms, had never heard of the Chitauri.  Dr. Strange, whose job it is to monitor threats, didn't know about Thanos.

Space is **big**.