On the contrary.
The walled gardens have not gone away with the fediverse. At all.
In fact there are more walled gardens than ever before. Every #Mastodon instance is its OWN walled garden, in terms of discoverability. Search is cordoned off: you can’t find anything for the most part except whatever might have been posted to your own walled garden and only if recent.
Talk of “freedom” is lovely but the reality is Mastodon is like a spy agency with severely compartmentalized info.