The great thing about a character as long-running and as complex as Natasha is that there's room for so many different, even contradictory, aspects of her. She can be a hardass, but she can also be loving. She can be a loner, but she can also form deep friendships. She can have a firm code of ethics even if it doesn't line up with the Avengers' 100%. There's a big gray area between being another Punisher and being a toe-the-line Avenger, and a lot of interesting stories come from that place. She's not just one thing--right now, she experienced Hydra taking over the US, was killed by one of her best friends, and woke up undercover in the Red Room, so yeah, it makes sense that the stories they tell about her in 2018 are going to be dark. But in five years, she'll be in a different place, and she'll get different stories.