If you're in the EU, then yes, as "Right to be Forgotten" is a thing: https://en.wikipedia.org/wiki/Right_to_be_forgotten#European...
But in general I agree, the expectation of something remaining "private" and "owned by you" after you publish it on the public internet, should be just about zero. Don't publish stuff you don't want others to read/store/redistribute/archive.
Others have said it already but when you are posting here on a public website, I would argue that you are effectively consenting that your content is now available for consumption by site visitors.
"Site visitors" may include people, systems, software, etc..
I think it would be pretty impractical for every visitor to the site to have to seek consent from each poster before making use of the content. That would literally break the Internet.
The same way Google and others have been crawling and capturing all your public posts for decades to power their search engines. Now the data is being used to power LLMs.
Were you able to opt out of being part of the search index (and I don't mean at the site level with a robots.txt file)?
I think your choice here is "don't post on a publicly accessible website", unfortunately.