The dirty little secret is, without her character the films wouldn’t have been nearly as popular.
Despite what the Left would have you believe, (traditional) sex sells.
I seem to remember, Black Widow wasn’t even supposed to be in the Avengers originally, but Joss Whedon made the point to the powers that be that’d it’d be a bunch of guys hanging out on a ‘boat’ basically. She was sort of the token girl on the team, but I thought she did well, visually nice to look at and the whole professional/now celeb spy thing who was strictly business, solid enough.