Let’s talk about Natasha’s shift in civilian costuming between Iron Man 2 and the Avengers. In IM2 it was all expensive looking dresses and button-up blouses, tailoring and sophistication. In the Avengers, she preferred jeans-and-leather-jacket ensembles. This change up makes sense when you remember that in Iron Man 2 Natasha was dressing a part, to fit into the rich and famous world of Stark Industries. The later stuff is probably more indicative of MCU Natasha’s personal sense of style.
There’s a real problem that extends across spandex universes where people look at the costume and then try to transfigure it into something not quite a costume, and that is what our heroes wear in their day to day life. The Black Widow outfit is tight and black, ergo Natasha is condemned to a lifetime of leather pants and weird hourglass corsets. Nevermind that for many characters costumes represent true alter-egos, ways to express personality traits that they must repress in their workaday lives, nevermind that I’m pretty sure Spider-man’s costume is also tight and he’s not dressed perpetually for jazzercise. But, you know, Captain America is always wearing a blue shirt with a white star on it, Clint Barton can’t say no to purple. It’s all very literal and it results in some laughably terrible hero fashion.
But if you go beyond “it’s tight! and it’s black!” you can get actual hints as to Natasha’s maybe aesthetic. Her costume, and the clothing she wears, are simple and no-frills and give her plenty of space to hang a weapon.