People are overreacting to the Carol will be the strongest avenger statement. I do think that Carol is going to be the most powerful, but I also think that part of her story will be her learning how to use restraint when it comes to her powers. Shes not going to fly in and one punch thanos, but she is most likely going to play a key role in defeating him. I find it interesting that the same people who talk about how great the people behind the MCU films are have little no faith in the film that just so happens to be lead by a woman.
To add onto this further, lets take a look at what's set up here:
-They specifically left ALL of the Original Six Avengers alive at the end of IW. Every one of them, and Avengers 4 will likely be the last time that all of them appear in a film together.
-They kept characters like Ant Man, Valkyrie, etc alive as well.
-Thor has an axe that can cut through the power of the Infinity Gauntlet and wound Thanos (and it probably would have killed him to if Thor would have aimed for a different spot and not grandstanded so much).
-Etc.
Now taking all of this into account, is it easier to buy that it will take a team effort to finally defeat Thanos, or is it easier to believe that Captain Marvel will be the Mary Sue character who wins the day solo? Personally, I find the former to be FAR more likely than the latter.
Now could she act as an "equalizer" to a degree, sure. But that would make some level of sense, given that The Avengers and GOTG together couldn't stop Thanos, and now half of them are dead, including some of their strongest members (Dr. Strange, Scarlet Witch, Vision, etc).
So perhaps Carol will help even the odds, but I seriously doubt that she beats Thanos on her own. For example, perhaps she, or maybe her and Thor (with Stormbreaker) together are the ones who physically take on Thanos, while the others find a way to undo what he's done and neutralize the Infinity Stones power or something?
The point is, people are getting worked up over nothing right now.