IMHO, it's not the technology that's the problem - RSS is excellent for what it does. Or at least, for what it's used for. The disconnect happens at the worst place - subscribing. Browsers don't really support it (see Chrome's feed button removal, and now you have to get an add-on from the Chrome store to reinstate that functionality), few outside of geeky/nerdy circles even know about RSS, and that's why everyone thinks they have to replace RSS with something else.
See also the circular "E-mail needs to be fixed" non-problem.
Because you're comparing an open, royalty-free technology with something a company controls? Ask former 3rd-party twitter client makers how they feel about Twitter, Inc. these days ;)
On a grid-by-grid feature list it loses, but Twitter is EXACTLY what is used by millions of people instead of RSS. They subscribe to Regexp facts instead of an RSS feed of facts. Instead of CNN RSS they subscribe to CNN Breaking News, etc.
Can Twitter give me a full list of only headlines that link directly to the article? Not in any of the current clients.
Ok, I could write a new client that does that, and be limited by Twitter's API, to be cut off at any point.
And even if I had an information dense client I wrote for myself, does every website automatically post every article of theirs, headline only to Twitter, and refrain from any other postings or comments? Can't force them to do that.
Twitter is not a good replacement for a lot of the RSS use cases.
It's definitely not. RSS is great because nobody owns it. I can pull feeds from whatever websites I want. Don't need to worry about rate-limited (ie Twitter), or being banned by some algorithm (ie Google)
See also the circular "E-mail needs to be fixed" non-problem.