As with CSS modules (mentioned in another comment), I’ve never used ‘proper’ Atomic CSS, however I have developed a site made up of mostly single-purpose classes.
The good: It was incredibly quick and easy to get the site up and running, and maintenance was equally quick and easy. Virtually no need to touch the CSS, for the dev work is done in the template layer.
The not so good: understanding how styles are built up and applied to the HTML elements was more difficult than with BEM as there can be a huge amount of classes. Basically, it’s perhaps too noisy.
So in general I don’t have a problem with the approach, but — and this is a huge but — as long as developers use the correct HTML elements for the content. As I mentioned in the article, the same caveat goes for BEM. Being able to style stuff more easily and using semantic HTML is not an either/or. You can do both!
I find BEM a happy medium between the class overload of Atomic CSS and the associated troubles of believing HTML should be free of style hooks.