Substack—and the surviving blogs that aren’t on Substack—are still going strong, and I don’t think they’re going to go away. Maybe Substack as a platform might decline the way Medium has. But the “Eternal September” types are usually either functionally illiterate or don’t like long form reading, and social media is increasingly optimized for those people. If you actually take the effort to write down your thoughts in text, you end up filtering for people intelligent and diligent enough to choose the written word even when video and photo content is readily available.