No technology other than RSS has had more think pieces written proclaiming the death of RSS (2006, 2009, 2010, 2012, 2013) and the rebirth of RSS (2009, 2010, 2011, 2018, 2018, 2019).
Really Simple Syndication (RSS) is a protocol that lets you subscribe to website updates – e.g., new blog posts, podcasts, or anything else. Today, most podcasts are distributed via RSS.
This site has an RSS feed you can subscribe to. In addition, you can read RSS updates with an RSS reader (e.g., feedly).
It's hard to gauge actual RSS usage. Substack has recently launched an RSS reader; otherwise, there isn't a vibrant ecosystem pushing forward the protocol (the last protocol update was 2009).
Some unordered thoughts about the forces acting on RSS.
RSS readers act like email clients in how they render content via HTML. Unfortunately, email content isn't as rich as the JavaScript-powered web today. Maybe that's OK for email (and podcasts), but not for generic blog content.
Substack has revitalized the blogging movement by giving away free hosting and email lists, and a business model for supporting writers. As email newsletters grow, RSS is a decent alternative to an increasingly cluttered email inbox.
Commercial incentives work against RSS. The protocol competes with internet advertising models (Google search ads, Facebook feed ads) and subscription models. Walled garden content aggregation is significantly more profitable than free syndication (e.g., Reddit, Facebook)
RSS doesn't have a true sponsor. Netscape initially developed it. Later, Aaron Swartz led a redesign and fork. Yahoo designed the Media RSS specification. There's also been some political strife with the RSS Advisory Board.
Creator incentives work against RSS. The protocol does not benefit content creators because it doesn't give them any insight into their audience (number of subscribers, emails, or other data).
RSS is one-way publishing; there is no way for content creators and their audience to interact (e.g., through comments or replies).
Curation and discoverability are more difficult on RSS than on native platforms. Of course, you can build this into the reader, but that requires scale to get good signals (scale only available to the internet advertising companies).
RSS had usability issues – discovering a feed and seeing raw XML was too technical for the average user.