Hmm in theory I get that, but in practice it’s not always easy to grasp.
When Fediverse stuff comes up as an “alternative” it’s often depicted as “leave Instagram, join Pixelfed” … not “join pixelfed.social” or “join pixelfed.de” … it’s often presented as if the instance you choose doesn’t matter that much. Which, is now pretty clear to me, is not true at all. It also seems a bit at odds with the idea of decentralization because if you want your content to be seen there’s a big incentive to join an already-large instance.
Apart from that, as a practical consequence, it’s hard to understand why, when and where you see something … like, a common point of criticism about corporate social media is that algorithms boost content in often hard-to-understand ways … but in the Fediverse, it just seems a different kind of intransparency, as long as you don’t just stick to your local instance.
I guess whether it’s a flaw or not depends on your expectations … definitely feels like a big drawback to me …