The problem is how to find people to follow. Twitter, as a centralized service with a search feature solves that problem in a way that individual sites with RSS feeds can't. Someone I've never interacted with can add a hashtag to their post on Twitter, and I can search for that hashtag, and find their post. If I've never interacted with someone, how do I know to go to their webpage and connect to their RSS feed?
This. The problem is not how many legs the internet stool has, it's the problem of discovery in the "dark forest".
You want people to be able to find you, for your outbound communications (self-promotion), and you want people to be able to cold-contact you in circumstances that are useful to you. But if you're not very careful your inbound communications get completely overwhelmed by spam and/or abuse.
Discovery is work. Spamblocking is work. Abuse deletion is work. None of which people want to do themselves, so they delegate it to platforms which do it for them.
I use standalone feed readers; some people use aggregators that have their own web interfaces.
RSS is my primary way of following the web these days (well has been for a couple of decades). If there's no RSS feed I simply don't follow a site; there usually is.
