I’m not sure I understand why this is a problem. RSS is a spec for publishing a list of available content, or publishing the content directly. Formatting that content was always going to be something people wanted to do, so whether it was rich text, html or what became markdown, it was inevitable that aggregators were always going to have to deal with both publishes wanting their publication to have styles and users wanting their aggregator software to either handle that style or hide it.
At least with a cdata tag your being explicitly told “here be dragons”
I see people stuffing all sorts of HTML tags and nonstandard attributes in an RSS <description>, just because CDATA allows them to do so without breaking the parser. Images, videos, inline SVGs with maybe some scripts inside...
The RSS spec should never have allowed this. Reading a feed would have been much more pleasant (not to mention safer for everyone!) if the contents were required to be in plain text.