Is It Dystopian or Post-Apocalyptic?

Came across this article that provides an excellent illustration of the difference between dystopian and post-apocalyptic themes. Apparently, I'm not the only one guilty of using them incorrectly and interchangeably. Here's my take in simplest terms: Post-apocalyptic will tell about the people trying to survive in a broken world, in the aftermath of some catastrophic event. Dystopian portrays a supposedly perfect, but oppressive society, where laws and lifestyles are imposed upon its people in an attempt to prevent returning to that hellish and broken world. So ... post-apocalyptic first, dystopian second!

https://www.goodreads.com/author_blog_posts/3926848-dystopian-versus-post-apocalyptic-literature