Earlier quoted context omitted.
What do you mean “you own your newsletter”? Your newsletter is owned by a massive corporate platform such as Mailchipm, which will ban you for wrongthink/wrongspeak just like other massive corporate platforms like Facebook. Just the first news story I found: https://www.nbcnews.com/news/amp/ncna1017221 - keep in mind that “antivaxxer” doesn’t mean what it used to mean but could simply mean you’re pointing out that va…
You're conflating the medium (newsletter) with its distribution mechanism (mass mailing). If you have the content and the destination addresses, it's trivial to switch to another provider.
Switching providers sometimes requires all existing subscribers to “opt in” again.
Regardless you’re still owned by a platform. Gmail ain’t gonna let you deliver 1000s of emails yourself.