I'm afraid you will have to skip reading articles whose background is dark. Some readers (and writers) need to have a dark background with white text so they can read. This is the case with people who have cataracts and other eye conditions.

I think you should suggest to Medium's new CEO that the platform make it possible for readers to specify how they prefer to view the site (in dark mode or light mode). Facebook does this, and Livejournal used to.