Most people in my circles understand "intersectionality" to refer to exactly the claim you're disputing, that it's good to identify and focus on an exponentially expanding amount of subgroups. I don't think this is an unreasonable interpretation - the Center for Intersectional Justice, a large nonprofit in the area, says one example of intersectionality (https://www.intersectionaljustice.org/what-is-intersectional...) is that you shouldn't attempt to address the gender pay gap without also thinking about race, socioeconomic status, and immigration status.