Well Usenet, RSS, and mailing list are there to use
- They are hard to use for regular people due to lack of modern and intuitive clients.
- They are somewhat hard to discover and learn. For example, browsers don't indicate the presence of RSS feeds without plugins anymore.
- Security and encryption are an after-thought, if any
Almost all of the above are due to the stagnation of their development (protocols and clients) due to emergence of easy-to-use, but centralized alternatives. They are not good modern options as they are now. But they are good models to build more modern alternatives on.