It may make things simpler for the user, but at the cost of storage and performance of every instance in the index, which won’t scale well as more instances are added over time. I personally think it’s better the way it is. As long as you are educated enough to know how to federate with other instances you choose to federate with, you can keep your own instance minimally connected to only the instances and communities you actually care about.

Maybe a good compromise would be for such an idea as a globally replicated index, to be optional, so individual instances could keep it disabled if they wanted to. If you choose to enable it as an instance owner, the pain points for your end users go away, at the cost of performance and other potentially negative side-effects. If you choose to keep it disabled, you can still federate with any instances you want, but you won’t participate in the index. Or maybe your instance would be listed and replicated to other instances’ indexes, but your own instance won’t receive updates as the global index continues to grow. Since it would just be for convenient discoverability, there’s not really any problem with that. No functionality would be lost for your or any other instance.

I think for a platform like this, in any case, a little bit of extra user education goes a long way. We shouldn’t be too afraid of expecting end users to educate themselves a bit, and we shouldn’t be too eager to hold their hands every step of the way. It makes for more adept end users and a healthier overall community, in my opinion. It’s like encouraging movie lovers to get off the couch and exercise once in a while.