That's what happens when we abandon protocols (RSS feeds) in favor of walled gardens.
Yes, in general terms, there's always an abstract discussion about RSS vs Facebook,Twitter,Google AMP, etc.
However, your particular comment is not relevant to this particular blog post. The RSS protocol is "free" but that doesn't matter if it does not address the targets that Facebook does.
(Besides that, the journalist writes for DennikN and they didn't "abandon" the RSS feed. It's at: https://dennikn.sk/rss-odber/)
We can't just reflexively reply with "RSS" every time the trigger word "Facebook" comes up. It needs to be relevant. RSS is not applicable to what the journalist is talking about. RSS is not relevant to the perspective of the publisher for metrics of "audience reach". RSS feed is a convenience tool for the reader and the blog post isn't about that perspective.
Ars Technica still does this, and it strikes a good balance between letting the user see what content is available in the tool of their choice (and whether they'd be interested in reading more), and the site/publisher having control over how the complete articles are presented.
Of course, this requires the site to actually have more than a paragraph worth of actual content for any given article.
Social functionality might not be important to you, but it is very important to many, many people.
(Services that graft social functionality onto RSS feeds could satisfy the same need, but then we're not talking about RSS feeds anymore...)
So the argument still stands. RSS was a much better mechanism to distribute updates and could have been made "social" if companies like Twitter and Facebook weren't intent on dominating that space.