Endgame Have Given Us A Much More Intimidating Captain America?

Here is the real question regarding Captain America losing his cool: is it uncharacteristic? Or is it precisely what the character needs to feel more real? His anger is almost certainly justified, as he and everyone else lost half of the world. However, he’s never been the type to lose his cool. The closest he ever got to doing so may be on the helicarrier in “The Avengers” while arguing with Tony Stark (Robert Downey Jr.). But in the end, Steve Rogers’ calm and collected demeanor is one of the main reasons he is the best possible leader of the kind of personalities who make up the Avengers.
Having said that, is it realistic? We know that Cap makes mistakes. He should have told Stark about Bucky (Sebastian Stan) and his involvement in his parents’ murders, and he probably should have seen more of the corruption within S.H.I.E.L.D. long before they almost launched their endgame. Briefly losing his cool at Scott Lang seems to reveal the missing piece of his personality. The man has been through some of the worst things anyone alive has ever seen. He saw WWII with his own eyes. He lost his parents, his friend, and three-quarters of a century. It stands to reason that he would almost certainly have a hard time managing his emotions from time to time, even if we never see it happen on camera.
In any case, the passage in “Look Out for the Little Guy” gives us an idea of the extra insight we can expect from the book, including making one of the best characters in the MCU feel more grounded and realistic. But is that who Cap should be?