I have now seen 15 movies in the Marvel Cinematic Universe. My response to those films is so predictable that I wonder if I'm human or just a cyborg who likes movies. I have given 12 of those movies a rating of 7/10. (Black Panther is a 9/10, and I didn't care for the Guardians of the Galaxy movies.) This is thrown off a bit because my favorite Marvel properties of the last couple of decades include the TV series Agent Carter and Agents of Shield, and I loved Spider-Man: Into the Spider-Verse, and apparently none of them are part of the MCU.
Black Widow was just as good as the other Marvel movies. I liked it partly because it was very un-superheroish. It was more like an action/spy movie, with car chases instead of battles between Iron Man and Thor or whatever. Scarlett Johansson was great, as usual, and Florence Pugh was good, as well, which made me glad, because we watched her in a movie last month that stunk (Midsommar), although she was the best thing about that one. It was clearly time for Natasha Romanoff to get her own movie ... well past time, given that even Ant-Man has already gotten two features. With the possible exception of Robert Downey, Jr., Scarlett Johansson is the biggest star in the Marvel universe, but as often as not she's treated as eye candy more than anything else. So just the fact that she and Florence Pugh are at the center of Black Widow is progress, much as Brie Larson's box-office bonanza performance in Captain Marvel mattered beyond the billion-dollar-plus box office for that movie.
None of this would matter if the movies were bad, but, as noted, both of those films are as good as their Marvel counterparts. Johansson has two Oscar nominations, Pugh has one, and Larson actually won an Oscar ... these are accomplished actors. But they are also believable in the ass-kicking mode required of them in the Marvel films.
The plot isn't as important as the back story of Natasha and her sister ... something about an evil villain trying to take over the world ... like I say, Black Widow would fit into the James Bond universe as easily as it does the MCU. Johansson and Pugh make their story worth our attention.
One note about the special effects. We saw the movie in IMAX, partly because there are 22 minutes in the film designed specifically for that format. It was impressive, but I was working at a disadvantage: I'd had surgery for a detached retina only two weeks earlier, and so I was watching with only one good eye. Honestly, I think the giant IMAX screen helped, but it will be fun to see Black Widow again sometime when both of my eyes work.[Letterboxd lists: Geezer Cinema, Film Fatales, Marvel Cinematic Universe]