Unfortunately, this decentralisation of basically what used to be 1 thematic sub into multiple clones "because it's technically possible" is just not what most users are looking for. That is why Reddit was ONE website with such a large amount of knowledge. The human brain likes to centralise stuff in one place. That is why when we put away stuff and clean our own homes, we tend to put all the forks together, all the knives together, all the glasses together... Centralisation is a way to break down complexity of what would otherwise be chaos, by factorizing it.
If you've got 50 different "gaming" instances instead of one, basically the very "gaming" word becomes irrelevant, and users will have to memorise the names of the 50 different hosting instances instead.
Also, on a pure tecnical standpoint, the "federation" aspect is currently simply not true: I get "The magazine from the federated server may be incomplete. Browse more on the original instance." warning message when I try to access most magazines that are not hosted on kbin.social.