Closed vs. Open Platforms

In a "closed platform" the connection of the content creator with the audience is controlled by the platform itself. For example on YouTube, there's no way to migrate your subscribers to another video sharing site. It doesn't matter how many subscribers you have, most viewers primarily see recommended videos, an aspect you have limited control over.

In an "open platform" content creator has a direct connection with the audience. You can take your email list, RSS feed, and customer list anywhere you move. Substack (email), WordPress (RSS), Patreon (membership) are good examples.