I'm not talking about CMS or blogs though, I mean individuals that are active on twitter. Redigit, the developer of Terraria doesn't have an RSS feed but is active on twitter. Valheim devs often post sneak peaks of upcoming updates on their personal twitter accounts. Rebecca, creative director of warframe is active on twitter. Lots of twitch streamers or youtubers don't have separate blog posts or sites, they just post on twitter about upcoming streams, videos or events. Webcomics and artists might have their own sites but generally its easier to discover new ones on twitter where they also often retweet other similar artists.

It's probably different for academia and businesses but for me, a completely casual user that doesn't contribute to twitter and instead just has a highly curated feed of things he likes, twitter was perfect before they started filling the feed with random crap I'm not even following. It doesn't seem to me like RSS is a replacement for that.