This lack of features led us back to email newsletters with businesses like Substack shining in it.
Yet, email is restrictive, unorganized, and its html support is cryptic at best. It also in the control of the sender (push) unlike RSS that is under the control of the receiver (pull).
Do we have an RSS alternative that adds authentication and other features to allow for the decentralization of email, with modern features enabled by smart RSS readers?
https://daringfireball.net/2005/02/feed_authentication
What are the "other features" you need for your use case?
But you can embed ads in RSS feeds if you want to annoy people.