Jerboa

It doesn't matter what instance you join if every instance also employs no blocks.

At this point in time it is starting to matter. With the increased instance level blocks and defederation.
In the future it won't matter as you will have mobile/web apps that create multiple accounts on the instances you want that have the communities you want to subscribe too.

If the communities are only created on the big instances, and the big instance decides to defederate from your home instance then you no longer have any way from your home instance to get access. Thus the future features I have alluded to become a real need.

Op made a valid point, if small niche groups form around small instances, you will have less issues and the instance will be for everyone who wants to join that community. Then it would truly be a decentralized platform where each instance is one or two communities. An instance block would not have the blast radius. For example, I don't think anyone who is small has the ability to block Lemmy.world . They are too big and have too many communities. If you were to block them you would need to setup the communities on your own instance. Whether that works or not and whether enough people join around it who knows.

Like you said tho, a community on a small instance had less chance for good visibility and being found. But that is where third parties come into play like browse.feddit.de. without them the early migrations would have struggled and community discovery would also have been an issue too.

Now that I'm thinking about it, if we could integrate the feddit browser into all the lemmy instances so when you search on your local instance it would show all items not just ones your instance knows about... That would help solve part of the discovery issues... Brb I need to chat with the feddit admins :p