There are a couple I have in mind. Like many techies, I am a huge fan of RSS for content distribution and XMPP for federated communication.
The really niche one I like is S-expressions as a data format and configuration in place of json, yaml, toml, etc.
I am a big fan of Plaintext formats, although I wish markdown had a few more features like tables.
RSS works great for me though.
I have an app on my not-so-smart phone to read news when commuting. It is not a long journey so I just want to have a quick glance at the headlines and read the actual articles that I want to. There are only 6 sites that I am interested, but still will take quite some work to crawl from the proper websites. RSS in turn is unified so I don’t need to worry about their website layouts, formats, etc. It also gives me an URL to the actual content which I can use readability/reader mode library to parse and further reduce unnecessary contents.
Quite the opposite, I hope more informational sites offer/keep RSS! (Some removed RSS typically after a revamp, design change)
Mastodon offers rss for both keywords and users